1/40 = .025, just multiply this by 21 and you have your answer
.525
-3x + y = 1 ............. the general form is y= mx +b .................y = 1 + 3x
...........................
Y = 3x + 1
(5 3/10) (m) + (5 3/10) (m) + (5 3/10) (m) + (5 3/10) (m)
P = 53/10 + 5 3/10 + 5 3/10 + 5 3/10
P = 53/10 + 53/10 + 5 3/10 + 5 3/10
P = 53/5 + 5 3/10 + 5 3/10
P = 53/5 + 53/10 + 5 3/10
P = 159/10 + 5 3/10
P = 159/10 + 53/10
P = 106/5
P = 21 1/5 meters
Answer: 21 1/5 meters (Decimal: 21.2m)
Hope that helps!!!! Have a great day!!!! : )