Really need help.

Question

A computer store sold 1250 desk top computers and 740 laptop computers this year. The number of desktop computers sold has been decreasing by 50 computers each year. The number of laptop computers sold has been decreasing by 40 each year. Suppose the yearly change in number of each type of computer sold continues, how many years until the number of desktops sold is equal to the number of laptops sold?

Answer 1

1250-50x=740-40x

1250-740=50x-40x

510=10x

x=510/10

x=51 years