Idon't care about the actual answers, but i really need knowing how to do this ?

If something is discounted 20% then you are only paying 80% of the original price.
100% price - 20% discount = 80%
now you are also paying an additional 8.25% sales tax. Then 80% + 8.25% = 88.25% of the original price is what you've paid.

0.8825x = $25.10

You can find the area of a rectangle by multiplying the length and height. so multiply 1/2*7/4(which is the simpler version of 1 3/4) and you get 7/8 as your answer.