How to solve -3x-6y=3 and 2x+7y=-17 using elimination method PLEASE SHOW WORK

Given sin28.4=.4756, cos28.4=.8796, and tan28.4=.5407 find the cos of 61.6

Do one of the following, as appropriate: (a) find the critical value z subscript alpha divided by 2 , (b) find the critical value t subscript alpha divided by 2 . 99%; nequals 17; sigma is unknown; population appears to be normally distributed.

Real gross domestic product: a) will increase if the price level increases. b) can change from one year to the next even if there is no change in output. c) will increase if the level of output increases. d) is a measure of inflation.