X = 15
X + 90 = 7x
X = 7x - 90
X - 7x = -90
-6x = 90
Divide both sides by -6
X = 15
Your answer is A. You literally plug in the numbers for a and b to solve for the equation.
G = - h/3 + 11/3
H = 11 - 3g
I hope this helps
(a)
we are given
the price of apple suddenly up by $0.75
Let's assume original price be 'p'
we are given
Sam bought 3 pounds of apple at the new price total is $5.88
so, new price = old price +0.75
price of 3 apples 
we are given that price is 5.88
so, we get equation as
.......Answer
(b)
Since, original price is p
so, we have to solve for p




so, original price is $1.21 per pound........Answer