What is the answer to 7a + 21b + 42c?

This needs to be done quick you are studying different function tools and begin working with this function y=-160-9(x) use the equation to answer the question y=-160-9(x) what is the y value when x equals -13? y=-160-9(x)

Sundar used linear combination to solve the system of equations shown. he did so by multiplying the first equation by 5 and the second equation by another number to eliminate the y-terms. what number did sundar multiply the second equation by? 2x+9y=41 3x+5y=36

Ireally need subtract and simplify.(-y^2 – 4y - 8) – (-4y^2 – 6y + 3)show your work, ! i will mark you brainliest but you have to show your work.