Both legs of the triangle are equal, with it being an isosceles triangle. You can tell the base is not equivalent due to there being the little arrow symbol on the base and not the legs.
To solve for x, add up the values on both legs and solve the equation from there.
Equation - 2x + 10 = 40
Subtract - 2x = 30
Divide - x = 15
To make sure you have the right answer, check your work.
