15. If S., S₂, S3, Sm be the sums of n terms of m A. Ps, whose first term as well as the common differences are 1,2,3, , m respectively;
show that S; + S2 + S3 +
+Sm
(m +1) (n + 1).
4
mn
=​

Find the solution of this system of equation -7x+y=-20 9x-3y=36

The ph level of a blueberry is 3.1 what is the hydrogen-ion concentration [h+] for the blueberry

Mario is constructing a frame for 10 in. by 8 in. photo. he wants the frame to be the same with all the way around in the same area of the frame and photo to be 120 square inches what is the dimension of the frame?