`a)` `205 - 7 . (x + 5) = 100`
`7 . (x + 5) = 205 - 100`
`7 . (x + 5) = 105`
`x + 5 = 105 : 7`
`x + 5 = 15`
`x = 15 - 5`
`x = 10`
`b)` `14x - 40 = 4^2 . 4^0`
`14x - 40 = 4^2`
`14x - 40 = 16`
`14x = 16 + 40`
`14x = 56`
`x = 56 : 14`
`x= 4`
`c)` `4 . 5^2 - x : 2^3 = 91`
`100 - x : 8 = 91`
`x : 8 = 100 - 91`
`x : 8 = 9`
`x = 9 . 8`
`x = 72`
`d)` `(5^2 . 23 - 5^2 . 13) . x = 10 . 5^3`
`(5^2 . 10) . x = 1250`
`250 . x = 1250`
`x = 1250 : 250`
`x = 5`
