Question

solve the system of equations below by using substitution
x + y = 30
y = 9x.
x + __ = 30
__ = 30
x = __
y = 9 x __
y = __
solution is (__, __)

Answers: 10, 30, x, 18, 12, y, 3, 9x, 10x, 2x

Answer 1

Substitute y = 9x into x + y = 30:

x + 9x = 30
10x = 30
x = 3
y = 9·3
y = 27

So the filled blanks are: x + 9x = 30; 10x = 30; x = 3; y = 9·3; y = 27. The solution is (3, 27).