An isosceles triangle is a triangle with two equal sides. Since, one of the angles is 90 degrees. Then, the 2 remaining must equal 90 because the total of the triangle should be 180 degrees. So, I think 45 degrees is the only one we can use here because 45 + 45 = 90 degrees.
Answer: Ok so when he starts with one month he has $1600 each month and add $500x for example for the second month add another $1600 and $500x and so on the x stands for however many cars he sold that day