let

x = the number of cars that Jane sells

y = the number of cars that Melissa sells

Jane sell 8 times as many Volvos as Melissa:

x = 8y

the difference in their sales is 35:

x - y = 35

by solving the system of equations:

x = 8y

x - y = 35

we find:

x = 40 cars

y = 5 cars

click here to see the step by step solution of the system of equations:

Jane sold 40 cars.