This is written as:
21 - 2(10 - 3^2) + 4 and is an expression, not an equation.
The work inside ( ) must be done first: 21 - 2(10 - 3^2) + 4 => 21 - 2(10 - 9) + 4, and, continuing, this gives us 21 - 2 + 4. That sums up to 23 (answer).
Answer:
a) -3x -2y = 12
b) 10x = -15y + 60
c) 6x +9y = 18
