`3^x . 3=243`
`=>3^x=243:3`
`=>3^x=81`
`=>3^x=3^4`
`=>x=4`
__
`7.2^x=56`
`=>2^x=56:7`
`=>2^x=8`
`=>2^x=2^3`
`=>x=3`
__
`x^3=8^2`
`=>x^3=64`
`=>x^3=4^3`
`=>x=4`
__
`x^20=x`
`=>x=0`
__
`2^x-15=17`
`=>2^x=32`
`=>2^x=2^5`
`=>x=5`
__
`(2x+1)^3=9.81`
`=>(2x+1)^3=3^2 . 3^4=3^6`
`=>(2x+1)^3=(3^2)^3`
`=>2x+1=9`
`=>2x=8`
`=>x=4`
