Question

Peter Mabel sold a total of 400 Oatmeal ($1.50) and Wheat
($2) breads during the Labor Day weekend. How many of
each did Pete sell if total sales were $700?

Answer 1

Sold:
X Oatmeals.
(400-X) Wheats.

3x/2 + 2(400-x) = $700.
Multiply both sides by 2:
3x + 4(400-x) = 1400
3x + 1600 - 4x = 1400
-x = 1400 - 1600 = -200
X = 200.
(400-x) = 400 - 200 = 200.

NOTE: 1.50x = (1 1/2)x = (3/2)x = 3x/2.