When should you use multiplication to solve a system of linear
equations by elimination

To use the elimination method you need the same variable in each equation to have the same coefficient. If neither variable has the same coefficient in each equation, you need to multiply one or both of the equations by a constant to get the same coefficient.

The key is the word about, they want an estimation.63 is closer to 60, 71 is closer to 7060 + 70 = 130ryan counted about 130 birds