Hi Ron, Stacey, Can we calculate like this: 10x+2y=5Z or 5(x+y) 1. y=10 sufficient to know x 2. z=(x+y)=16 sufficient to know x Therefore, D. yes, that's an excellent way to do it. BUT DO NOT, EVER , LEAVE THE SAME VARIABLE ON BOTH SIDES OF A LINEAR EQUATION. in this case, this means that you shoul...