The cost of 1 one gallon of gas is $ 2.5
How to find the cost of one gallon of gas
The cost of one gallon of gas is solved using the equation of the graph
The equation graphed is written in the slope intercept form s below
y = mx + c
where
m = slope
b = y-intercept
The slope, m is calculated using the points on the graph (4, 10) and (8, 20)
m = (y₀ - y₁) / (x₀ - x₁)
m = (10 - 20) / (4 - 8)
m = -10 / -4
m = 5/2
Using point (4, 10) and the point - slope formula we solve for b
y - 10 = m (x - 4), m = 2.5
y - 10 = 2.5x - 10
y = 2.5x
For 1 gallon, substitute x = 1
y = 2.5 * 1
y = 2.5