Solve by elimination

3x + 5y = -1
7x - 5y = 31

Darian wants to build a regulation size pool table that is 9 feet in length.he plans he ordered are 18 by 36 inches. what is the scale factor of the dilation he must use to build a regulation pool table

Extra points! find the missing dimension! need asap

How many times larger is 6 × 10^12 than 2 × 10^7? a. 30,000 b. 3,000 c. 3,000,000 d. 300,000