Find the value of x in the equation

10.5 (equivalent to the fraction 21/2)

To get this answer, you set 10x-15 equal to 90 and solve for x. The reason why these two angles are equal is because they are vertical angles.

10x-15 = 90

10x-15+15 = 90+15 add 15 to both sides

10x = 105

10x/10 = 105/10 divide both sides by 10

x = 105/10

x = 21/2 is the answer in fraction form

x = 10.5 is the answer in decimal form