Answer:
x=2y/7
Step-by-step explanation:
y=7x^1/2
7/2x=y
7/2x/7/2=y/7/2
in the forth line of the equation it should be this
-6x+10=4x+20
-6x-4x=20-10
-10/-10x=10/-10
x=-1
-20n^2-39n-15
