Answer: 1/4 of a minute to drain 18 litres of water ( 15 seconds)
Explanation:
find slope or rate using two points on the line.
(0, 360) and (5, 0) and use slope formula y2- y1 over x2-x1
0 - 360 over 5 - 0 = -360/5, reduced to -72 rate
m = -72
b = 360
x = time
y = 360 - 18 drained = 342
y=mx + b is your slope intercept formula
342 = -72x + 360
subtract 360 from both sides
342 - 360 = -72x + 360 - 360
simplify
-18 = -72x
divide both sides by -72
-18 / -72 = -72/-72 x
simplify
-18/-72 = x
reduce your fraction
1/4 = x
so 1/4 of a minute or 15 seconds to drain 18 liters of water