Consider that x = 1.5 and y = 3. which statement is true about x + y?

Without the statements all we can say is x+y=4.5

The triangle has sides "a", "b" and "c", where side a = side b and the hypotenuse (side "c") equals side "a" or "b" times the square root of 2.

Prism volume = triangle area * height
342.1 = triangle area * 13.2
triangle area =  342.1 / 13.2
triangle area =  25.9166666667

area of a triangle is (1/2) base * height
In a 45 45 90 triangle, the base = height and since we don't know either the base or the height we'll call both "x".
So triangle area = (1/2) * x^2
25.9166666667 = (1/2) * x^2
x^2 = 51.8333333334
x ( the base and the height) = 7.1995370222  
the hypotenuse of a 45 45 90 triangle = leg * square root (2) =
hypotenuse = 7.1995370222 * sq root (2)
hypotenuse = 10.1816828995

So, one of the legs = 7.1995370222

Source:
http://www.1728.org/triprism.htm