The form of the linear equation is y = mx + b
m is the rate
b is the y-intercept (initial amount)
Since y represents the mass of the gas
Since x represents the time
Since the rate of leaking is 1.5 gram/min
Then m = -1.5
Since after six minutes the gas left is 60 gram
Substitute m in the form of the equation by -1.5 and use (6, 60) to find b
y = -1.5x + b
We use the rate negative because the value of gas has become less
Substitute x by 6 and y by 60 to find b
60 = -1.5(6) + b
60 = -9 + b
Add 9 to both sides
60 + 9 = -9 + 9 + b
69 = b
Substitute it in the equation
y = -1.5x + 69
The line's slope-intercept equation is y = -1.5x + 69