Create equivalent expressions in the equation that all have equal bases.
Since the bases are the same, then two expressions are only equal if the exponents are also equal.
Multiply each term in -y=3 by -1
Multiply each term in -y=3 by -1.
Multiply -1 by -1.
Multiply y by 1.
Multiply 3 by -1.
Solve for y 4^(-y)=64