Answer:
x=-7
Step-by-step explanation:
We are given the expression:
R=2x +9y
We want to find x when R=13 and y=3. Therefore, we must substitute the numbers in for the variables.
13=2x+9(3)
Multiply 9 and 3.
13=2x+27
Now we must solve for x by isolating x on one side of the equation.
27 is being added to 2x. The inverse of addition is subtraction, so subtract 27 from both sides.
13-27=2x+27-27
13-27=2x
-14=2x
x is being multiplied by 2. The inverse of multiplication is division, so divide both sides by 2.
-14/2=2x/2
-14/2=x
-7=x
x=-7
