E (2x)=15

How would i solve this?

Answer question above and explain each step : )

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

What is the sum of the geometric series in which a1 = 7, r = 3, and an = 1,701? hint: cap s sub n equals start fraction a sub one left parenthesis one minus r to the power of n end power right parenthesis over one minus r end fraction comma r ≠ 1, where a1 is the first term and r is the common ratio