Answer:
Take 5^x as y.
Now the question becomes a simple equation.
y + 20y - 125 = 0.
21y = 125.
Thus, y = 125/21.
Now resubstituting we get,
5^x = 125 /21.
Taking log on both sides,
xlog5 = log 125 - log 21
x = (log125/log5) - (log21/log 5)
x= 3- 1.89
