Solve for r.

K=5r-9s

r= (K + 9s) / 5

Solve for n.

18m+6n=-3

n=(-3-18m)/6

Solve for b.

r=(2+b)m

b= (r - 2m) / m

Solve for x.

4(x-h)=z

x = (z + 4h) / 4