1)2^x-5=16
2^x=16+5
2^x=21
x=log2 (21)
....................
2)7^x+7^x+2=350
2+7^x+2=350
2×7^x=350-2
2×7^x=348
7^x=174
x=log7 (174)
....................
3)16^x-17×4^x+16=0
(4^2)^x-17×4^x+16=0
(4^x)^2-17×4^x+16=0
t^2-17t+16=0
t=16
t=1
4^x=16
4^x=1
x=2
x=0