Alrighty
remember

means

and

and

for all real values of x
so

means

means

which simplifies to
1=x²+4x-5
minus 1 both sides
0=x²+4x-6
use quadratic formula or complete the square

and

2 solutions
T= Mins
1 hour = 60 mins
60 x 6 = 360
360 - T = x
X= How many minutes he has remaining