A washer and a dryer cost $780 combined. The washer costs $70 less than the dryer. What is the cost of the dryer?

Oh, be very careful about the "$87."

Let the dryer cost x.

Then, the washer costs (x+87)

Together, they cost  (x) + (x+87) = 787

        2x+87 = 787

           2x = 700           [subtract 97 from both sides]

            x = 350             [divide both sides by 2]

The dryer cost $350.

Check:   The washer cost $437.  Together, they cost $787  good to check, right?

Step-by-step explanation:

x/3-10=8

x/3=18

x=48