By the way, it's pi, not pie. just wanted you to know as you may lose marks in tests for spelling (but i may be wrong)
we know circumference is pi multiplied by the diameter.
the diameter is 2x the radius
we can re-arrange the first fact to get:
diameter (or 2x radius) = circumference divided by pi.
since the circumference is 24pi we can cancel off pi from the circumference (24pi) and pi.
now we have the diameter = 24
since the diameter is 2x the radius you divide both sides by 2 and get:
radius=12cm
Add 51 to get next number.
Proof:
5+51=56
56+51=107
107+51=158
If there are 8 groups of 65 students, that means they can seat 8*65 students total. 520 students
So based on your question about the line A and B meet and the four lines are congruent to each other. The graph doesnt show any measurements so there is no exact value to the length of X. But you must consider that the lines are proportional to each other so it means that they are congruent.