I would try drawing the line on a coordinate plane to help.
I think you want the least common multipule (exg LCM of 2,3,4 is 12)
so we find the factors and include all of them so like this
15=3 times 5
12=2 times 2 times 3
8=2 times 2 times 2
so to include all of them we include 3 2's, 1 3 and 1 5 or 2 times 2 times 2 times 3 times 5 or 8 times 15 or 4 times 30 or 120
the LCM is 120
so 4/15=32/120
1/12=10/120
3/8=45/120
add 32/120+10/120+45/120=(32+10+45)/120=87/120
X^2+ (y+8)^2 = 81.....this is C.
X^2 + y^2 + 16y +64=81 so x^2 + y^2 + 16y = 17.....this is D.
So I’d say C and D are correct
