Question

Each small kite costs $4, while each large kite costs $7. If the total money collected selling kites is $150, and 30 kites are sold, how many of each size kite are sold?

Answer 1

8 small and 22 large
10 small and 20 large
20 small and 10 large
27 small and 6 large

Answer 2

Rule #1 - Name Stuff.
Q1 - Name what?
A1 - What does it want? Name that.

S = Cost of a small kite
L = Cost of a large kite

Now, start translating the problem statement.