(8/16) would be the slope
You can buy 4 shirts because you bought one pair of jean (80 - 29 = 51) and so with the leftover money you could buy 4 shirts because (12 x 4 = 48) and then you'd have a leftover 3 dollars.
ANSWER
The required angle is

EXPLANATION
Let the angle whose sine is

be

Then

We take the inverse sign of both sides to obtain,

We use our scientific calculator to evaluate and obtain,
Answer:
30.8 miles per gallon
Explanation:
1.25 = 38.5
Divide both sides by 1.25
1 = 30.8