Hi!
Let's find out how much he has to pay for each of the deals.
Deal 1
£1.75 per mile.
192 x 1.75 = 336
£336
Deal 2
15% off of £680
680 x 15 = 10200
10200/100 = 102
680 - 102 = 578
£578
Deal 3
£90 per day - 1/10
90 x 7 = 630
1/10 of 630 = 63
630 - 63 = 567
£567
The cheapest deal would be Deal 1
Hope this helps! :)
-Peredhel