Please show me how to work this

e^.05t =1600

log = natural logarithm

log ( a ^ n ) = n * log ( a )

If your expression mean :

e ^ ( 0.05 t ) = 1600

then :

0.05 t * log ( e ) = log ( 1600 )

Remark : The natural logarithm of e = 1

0.05 t = log ( 1600 ) Divide both sides by 0.05

t = log ( 1600 ) / 0.05

Remark : 1 / 0.05 = 20

t = 20 * log ( 1600 )

t = 20 * 7.3777589

t = 147.555178