How do i set this trig problem up? PLEASE help me.

Find tan (s + t) given that sin s = 1/4, with s in quadrant 2, and sin t = -1/2, with t in quadrant 4.

sin s = 1/4 and s in II, ---> tan s = -1/√15

sin t = -1/2, and t in IV ---> tan t = -1/√3

tan(s+t) = (tans + tant)/(1 - tanstant)
= (-1/√15 - 1/√3)/(1 - 1/√45)

I will let you finish the arithmetic.