Today’s brain teaser might be the toughest one yet and will certainly get your brain cogs whirring. Anyone still feeling the effects of a big night out might need to wait a while before trying it because instead of being an optical illusion it involves maths.

If you can solve it within 15 seconds, and without having to brush off your algebra skills from school, then you have a high IQ.

But don’t worry if you have struggled because we will reveal the solution below.

All you have to do is work out how old the dog is today. It sounds simple enough but unlike optical illusion puzzles, there are no numbers to spot and no lines to count.

Instead of being helpful, the picture does not reveal any massive clues like a birthday cake with the correct number of candles on it.

Trying to work out exactly how old he is has left thousands of people scratching their heads in frustration as they look at the picture and try and figure it out.

Some people will have been able to instantly look at the question and work out the answer.

Everyone else should have one last go at trying to solve the problem before looking at the solution which is revealed below.

The question is, in two years the dog will be twice as old as it was five years ago, how old is the dog today?

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Let’s start by calling the dog Fido (this bit is not essential, but it seems like a good traditional dog name) and then, to find his age, we can first suppose that Fido’s present age is x.

Fido’s age two years from now will be x + 2 and his age two years ago was x – 5.

The question states that after two years, Fido will be twice as old as he was five years ago. This can be expressed as (x + 2) = 2 (x – 5).

Cast your mind back to school when you learned how to simplify equations because that skill comes in useful here.

By simplifying the equation, you get x + 2 = 2x – 10.

And then you need to find the part of your brain where you stored details about how to rearrange and simplify equations.

Once you have found it you’ll know to move the 2x to the start of the left-hand side of the equation and put the two on the other side.

This makes the equation become 2x – x = 10 + 2.

And now the easy part, adding 10 and 2 together equals 12 and that’s the answer. Fido is 12 today.

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Brain teasers like this may seem like they are just a brief distraction but some experts suggest doing just one or two a day could have benefits in the long run.

If you do them repeatedly alongside other mental exercises such as crosswords, this could help improve your brain health in the long run.

The brain is a muscle, and like other muscles in the body, it needs to be exercised. The healthier and fitter your brain is, the less likely you are to develop a neurodegenerative condition such as dementia.

While this isn’t to say that brain teasers will stop you from getting dementia, other factors play a role too, they could help keep your brain healthy.