If r = 3s + 1 and t = s - 4, then what is r in terms of t?

 
 
How do you solve for x?

a - c 
-------- = m
x - a

 
 
How would you solve this equation for y?
y + x = xy
 
 
Solve for x:

c - 1
-------- + d = cd
x
 
 
Solve the equation 4x - 2y = -12, for y.