The measure of the obtuse angle is the I saucily's triangle is 2 1/2 times the measure of one base angle right and solve a system of linear equations to find the measures of all the angles

Let o represent the obtuse angle, and let the base angle be represented by b. Then you have

... o = 2.5b

... o + 2b = 180

Substituting the first equation into the second, you have

... 2.5b + 2b = 180

... 4.5b = 180

... b = 180/4.5 = 40

... o = 2.5*40 = 100

The obtuse angle is 100°; the base angles are 40°.