Maths

The answer is 10w + 12X + 9Y

With maths in general start your answers by looking at the following:

1. are there anything that has to be X or / if no (as in your case)
2. are there anything that has to be - or +

Pretend their were no numbers in front of the letter… e..g w + x + y + w + x + y

What would you have done then? just added all the x’s and the y’s and the w’s

This is the same except there are no a number of them. so just once again add all the X (.I.e. 4X plus 8X) and do the same with the y’s

It’s difficult to explain over internet…but you can’t add X and Y, because you can’t add “apples and pears”