x = the number of miles
y = the total cost
Company A:
0.60x + 60 = y [Company A charges $60 plus $0.60 per mile(x)]
Company B:
0.90x + 30 = y [Company B charges $30 plus $0.90 per mile(x)]
To find the number of miles where the costs for both companies are the same, you can set the equations equal to each other as the costs(y) are the same:
y = y Substitute the equations into "y" (substitute (0.60x + 60) and (0.90x + 30) into "y" since y = 0.60x + 60 and y = 0.90x + 30)
0.60x + 60 = 0.90x + 30 To find x, isolate/get the variable "x" by itself. Subtract 30 on both sides
0.60x + 60 - 30 = 0.90x + 30 - 30
0.60x + 30 = 0.90x Subtract 0.60x on both sides to get "x" on one side of the equation
0.60x - 0.60x + 30 = 0.90x - 0.60x
30 = 0.30x Divide 0.30 on both sides to get "x" by itself
100 = x 100 miles
(if you need to find out the cost where both companies cost the same, you can substitute/plug in the value of x into one of the equations.)
0.60x + 60 = y Plug in 100 into "x" since x = 100
0.60(100) + 60 = y
120 = y At 100 miles, both companies cost $120
