Question

Need help with math work

Answer 1

Plug in x = 12 and y = -5 into the given equation:-

3(12) - 3(-5) = 36 + 15 = 51  Not 21

So (12,-5) is not a solution.

Answer 2

Review:  a "solution" to an equation is a numerical value (or set of values) that makes the equation true. 

Here you are given the linear equation 3x - 3y = 21 and the point (12,-5).  If x=12 with y= -5, then (12,5) is a solution of 3x - 3y = 21.

Substituting, 3(12) - 3(-5) = 21.  Is this true or false?

36 + 15 = 21 is obviously not true.  Thus, (12, -5) is NOT a solution of 3x - 3y = 21.