help I have already published it 3 times and nobody helps me, could someone help me and explain how to do it? Thank you​

The sum of two numbers is 12 and their difference is 18 what are the two numbers

X2 + y 2 = 36 x + y = 6 solve the system of equations.

Aprojectile is thrown upward so that its distance above the ground after t seconds is given by the function h(t) = -16t2 + 704t. after how many seconds does the projectile take to reach its maximum height?