Question

Can someone please explain?

Answer 1

This is an isosceles triangle. The angles at the base are congruent (they have the same measures).

Look at the picture.

We know: The sum of the measures of angles in a triangle is equal 180°.

Therefore we have the equation:

`2x-10+2x-10+3x+25=180` combine like terms

`(2x+2x+3x)+(-10-10+25)=180`

`7x+5=180` subtract 5 from both sides

`7x=175` divide both sides by 7

`x=25`

`m\angle A=2x-10\to m\angle A=2(25)-10=50-10=40\\\\m\angle C=m\angle A=40\\\\m\angle B=3x+25\to m\angle B=3(25)+25=75+25=100^o`

Answer: D. m∠C = 40