The answer and how to get the answer

Which of the fallowing best completes the sequence 5,10,15, a) 30 b) 22 c)25 d)35

Using the quadratic formula find the zeros of the given polynomial -5x^2+3x-11

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