20-1(tip) is 19
19-3 additional is 16
16/2 is 8
8 miles
Well you left $1 for tip and paid $3 for the taxi. So we can subtract $4 from the $20 which leaves us with $16. Then divide that by 2 which gives us 8. We divide 2 since it costs $2 for every mile.
The answer is 8 miles