To do this you need to work bout what 10% of 340 minutes is. To do this do 340 / 10 = 34 34 is 10% of 340. Now you should subtract the 10% from the original time. 340 - 34 = 306. The answer is 306 minutes.
That was the long method. The short method is to use percentage multipliers. To do this you do 340 x 0.9 = 306.
Either way you would get the same answer of 306 minutes.
