Question 1102904
The easiest way is to use the 2nd equation and solve for y. This avoids working with fractions.
Adding y to both sides gives 3x=16+y, and then subtracting 16 from both sides gives y=3x-16. 
Substitute this value for y in the first equation, getting 7x-9(3x-16)=-8. Multiplying you get
7x-27x+144=-8, then -20x+144=-8. Subtract 144 from both sides gives -20x=-152, then dividing both sides by -20 gives x=7.6.  Substitute 7.6 for x in first equation gives 7(7.6)-9y=-8, then multiplying gives 53.2-9y=-8 Subtract 53.2 from both sides leaves -9y=-8-53.2 or -9y=-61.2 Dividing both sides by -9 gives y=6.8 solution is x=7.6 and y=6.8
Check:  Substitute both values into each equation. 7x-9y=-8 or 7(7.6)-9(6.8)-8 0r 53.2-61.2=-8 0r 
-8=-8. Check!  In second equation 3x-y=16 substitute 3(7.6)-6.8=16 or 22.8-6.8=16 or 16=16 Check!