<PRE><B>Question 17066</B>
If as you say, {{{3y=6x+21}}} and {{{3y=-4x+31}}}, then 
3y = 3y, so
6x+21 = -4x + 31


It would be a nice idea to solve this equation for x, by adding +4x to each side:
6x + 4x + 21 = -4x + 4x + 31
10x + 21 = 31


Next, subtract 21 from each side:
10x + 21 - 21 = 31 - 21
10x = 10
x= 1


Solve for y next:
3y = 6x + 21
3y = 6(1) + 21
3y = 27
y= 9


Solution (1, 9).


Check:  Use the other equation.
3y = -4x + 31
3(9) = -4(1) + 31
27 = 27
It checks!!


R^2 at SCC</PRE>