5x-10=3x+40
This is because of the vertical angles theorem (vertical angles are always equal).
Now, subtract 3x from each side. Do this because you cannot have the same variable on two sides of the equation.
2x-10=40
(This is the subtraction property of equality)
Now, add 10 to each side
2x=50
(This is the addition property of equality)
Finally, divide each side by two.
x=25
(This is the division property of equality)
5(25)-10
125-10
115
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