Ineed the questions says to find ths y intercept aftet the line transforms 3 units down

That's easy

the y intercept is where it hits the y axis
that is how far up or down
so then it tells you to transform it 3 units down
just find the y intercept then minus 3 from it

ok
y intercept is where line crosses y axis or where x=0

so set x=0 and solve for y

6(0)+5y=-15
0+5y=-15
5y=-15
y=3 is the y intercept

translate 3 units down so
3-3=0
y=0 is the y intercept after transformation (should be translation)

Ithink if im not mistaking b is -3 but im not a 100% sude