Answer:
a) 2.5
b)2.33
Step-by-step explanation:
a)

Bring the numerals to the right hand side and the x terms to the left hand side

Simplify

Divide 3 on both sides, to get x

b)

Bring the numerals to the right hand side and the x terms to the left hand side

Simplify

2a+b4.....................
The answer would be rounded by 7
$16.80 / 4 gallons = $4.20 per gallon