Answer:
C = 2
Step-by-step explanation:

Isosceles right triangles are half squares, and if the length of one side is 6cm, that is the length of the other side since both segments are equal. Take the formula to find the area of a square (base times height), apply the side measurement of the triangle (6cm) and divide it in half to find the area of half of it (therefore, finding the area of the isosceles triangle.)
(6x6) / 2
6x6 = 36
36 / 2 = 18
The area of the isosceles triangle is 18 square centimeters.
If Heather can do 2 in 10 minutes, then that means that she can do 12 in 1 hour. If Joel can do 3 in 15 minutes, then it means that he can do 12 in 1 hour. Add the number of problems they can do total and that will go between 30 and 50. It is just "less than", not "less than or equal to" because you want to know when the total number goes between the numbers.
Therefore, the correct answer must be <span>30 < 24x + 5 < 50.</span>