Question

An isosceles triangle in which the two equal sides, labeled x, are longer than side y.
The isosceles triangle has a perimeter of 7.5 m.

Which equation can be used to find the value of x if the shortest side, y, measures 2.1 m?

2 x minus 2.1 equals 7.5
4.2 plus y equals 7.5
y minus 4.2 equals 7.5
2.1 plus 2 x equals 7.5

Answer 1

Perimeter: 2x + y = 7.5. With y = 2.1 that gives 2x + 2.1 = 7.5.

So the correct choice is: 2.1 plus 2 x equals 7.5. (Then x = (7.5 − 2.1)/2 = 2.7 m.)