This is just y = mx + b with two equations so
y = 0.15x + 39.98;
y = 0.13x + 53.98
Since y is equal to y and 0.15x + 39.98 = y, and 0.13x + 53.98 = y we can substitute y.
0.15x + 39.98 = 0.13x + 53.98
You need to use the subtraction property on both sides so
(0.15x +39.98)-39.98 = (0.13x + 53.98)-39.98
.15x + 0 = .13x + (53.98-39.98)
.15x = .13x + 14
Then subtract .13x from both sides
.15x - .13x = .13x - .13x + 14
.02x = 14
Simplify
.01x = 7
we want one x so multiply both sides by 100
(.01x)100 = (7)100
x = 700
700 miles is the amount of miles where the two slopes intersect or have equal values.
---> 700 Miles