Q1. p=a-i
Q2. l= 1/2p-w
Q3. t=d/s
I think that these are correct
 
        
             
        
        
        
4(2x5 + 3) - 4(2) + 2(5).
4(13) - 18.
52-18 = 34.
        
                    
             
        
        
        
Taxi A 
1mile £3.50+£1.75=£5.25
Taxi B
1mile £1.25+£2.00=£3.25
Taxi A
2miles £3.50+£3.50=£7.00
Taxi B
2miles £1.25+£4.00=£5.25
Taxi A 
3miles £3.50+£5.25=£8.75
Taxi B
3miles £1.25+£6.00=£7.25
Taxi A
4miles £3.50+£7.00=£10.50
Taxi B
4miles £1.25+£8.00=£9.25
Taxi A
5miles £3.50+£8.75=£12.25
Taxi B
5miles £1.25+£10.00=£11.25
Taxi A 
6miles £3.50+£10.50=£14.00
Taxi B
6miles £1.25+£12.00=£13.25
Taxi A
7miles £3.50+£12.25=£15.75
Taxi B
7miles £1.25+£14.00=£15.25
Taxi A
8miles £3.50+£14.00=£17.50
Taxi B
8miles £1.25+£16.00=£17.25
Taxi A 
9miles £3.50+£15.75=£19.25 (the same)
Taxi B
9miles £1.25+£18.00=£19.25 (the same)
^^^
They would have to drive 9 miles for the taxi to cost the same. 
Hope this helped, this is the longest way to work it out but also the simplest.
        
             
        
        
        
Find the area of the squares.
4 ×4 = 16
Find the area of the wall.
20 × 10 =200
Divide 200 by 16.
200 ÷ 16 = 12.5
You need 12.5 squares.