For some value d, an isosceles triangle has at least one angle of 2d-40 degrees and at least one angle of d+10 degrees. What are all possible values of d?
Either
2 ( 2d - 40) + (d + 10) = 180
4d - 80 + d + 10 = 180
5d - 70 = 180
5d = 180 + 70
5d = 250
d = 250 / 5 = 50
or possibly
2 ( d + 10) + 2d - 40 = 180
2d + 20 + 2d - 40 = 180
4d - 20 = 180
4d = 180 + 20
4d = 200
d = 200 / 4 = 50
d = 50
