Answer (4):
a=ub/k because
u=ak/b (starting equation)
ub=ak (multiply b to both sides)
a=ub/k (divide both sides by k)
Answer (6)
x=g+c-y because
g=x-c+y (starting equation)
x+y=g+c (add c to both sides)
x=g+c-y (subtract y from both sides)
