Corresponding sides have the same ratio, so
x/15 = 12/(12+8) = 3/5
x = 15*3/5
x = 9
To find a slope we have to use this equation:
(y2 - y1 )/(x2 - x1)
and we have two x's and y's
so we will put them in their places....so (1-(-5))/(4-2)
and we will get 6/2 which is 3
Its A.3
.............
2/6 is equal to 4/12 and 3/4 is equal to 9/12 so 3/4 is larger
These numbers are "a" and "b".
Sum is 64, so
a+b=64
Difference is 42 so
a-b=42
So you've got:

When a+b=64 and a=53 you've got:
53+b=64
b=11
So these numbers is 53 and 11.