Question 698107
STEP 1: 

Multiply each equation by a number that will create
 opposite coefficients for x. 
In this case we will multiply first equation
 by -7 and the second equation by 3; 
After multiplying we have the following system: 

-21x+14y=-147
21x+9y-285



STEP 2: add the two equations together to eliminate x from the system.
23y=138


STEP 3: find y 

y=6

STEP 4: substitute the value for y into the original equation to solve for x.

3x-2(6)=21
3x=33
x=11


add x+y and you get 11+6=17

Sorry about that, must have made a mistake somewhere!!!! :)