2x+5y-3x-(-9) for x=-9, y=-6
In this case, you are being asked to simplify an expression given values for the two variables involved in the expression.
The first step is to "plug in" the values for x and y into the expression. This follows the substitution property of algebra, where a value is substituted into an expression each time it "appears" in the expression.
So, when we substitute -9 in for x and -6 for y, we get this:
2(-9) + 5(-6) - 3(-9) - (-9)
Now simplify the expression, following the order of operations (PEMDAS):
-18 + (-30) - (-27) - (-9)
= -18-30+27+9 (Notice that subtracting a negative is the same as adding a positive.)
= -12
Hope that helps.