1.8^2x-8^x-56=0 16x-8x-56=0 8x=56 x=7 2.5^x+1+5^x=750 10x+1=750 10x=750-1 10x=749 x=749/10=74,9-7x 3.3^2x-1+3^2x=108 12x+1=108 12x=107 x=107/12=8,916