Leah is solving the equation below using the properties of exponents.
2^2x-3 =(1/16)^3x+9
here is leah's work:
line 1: 2^2x-3 =(2)^4(3x+9)
line 2: 2^2x-3 =(2)^12x+36
line 3: 2x-3=12x+36
line 4: -3=10x+36
line 5: -39=10x
line 6: -3.9=x

leah checks her answer and realizes she has made a mistake. on which line did leah make a mistake?
what was leah's mistake?