A triangle has a total internal angle of 180. The three angles have sizes of a, (a-20) and (½ a). Find the size of angle a.

Answer 1

All 3 angles should add together to equal 180 so

a + a-20 + 1/2a = 180

(combine like terms)

2.5a -20 = 180

(20 is being subtracted from variable a so we will do the opposite and add 20 to each side of the equal sign)

2.5a = 200

(a is being multiplied to 2.5 so we will do the opposite and divide by 2.5 on each side of the equal sign)

a= 80 degrees