I need help with #18 & 20 ASAP
Please explain so I can understand

Write numerical coefficient of y² in the expression 2x² - 15xy – 7y²

Solve the following simultaneous equation by using an algebraic method (either substitution or elimination) 2x + 3y=-4 4x-y=11

The first side of a triangle measures 5 in less than the second side, the third side is 3 in more than the first side, and the perimeter is 17 in. how long is the third side? if s represents the length of the second side, which of the following represents the length of the third side? s-5 ws-2 s+ 3 next question ask for turn it in