Can someone help me with this question?

Determine the exact value for each trigonometric expression, given sinA= 4/5, cos B= (-8/17),

[(pi)/2]<A<pi and (pi)<B<[3(pi)/2]

Find

1) sin (A-B)

2) Sin (A+B)

3) cos (A+B)

4) tan (A-B)

if you could just tell me one of the answers and how you got to it, i can probably figure out the rest. thank youuuuuu!!