What two numbers can multiply to get +15, however, add together to get -9?

Need on this one asap im almost done with this subject

Explain how you can use the associative property to evaluate (7x50)x4.

The value of x in this system of equations is 1. 3x + y = 9 y = –4x + 10 substitute the value of y in the first equation: combine like terms: apply the subtraction property of equality: apply the division property of equality: 3x + (–4x + 10) = 9 –x + 10 = 9 –x = –1 x = 1 what is the value of y?