-19m-19 = 4m-4m+19
-19m-19 = 0+19
-19m = 19+19
-19m = 38
m = 38÷(-19)
m = -2
Remark
This is an arithmetic progression. You have the first and last terms and the difference.
Givens
a = - 18
L = 60
d = 4.5
Equation
L = a + (n - 1)d
Solve
60 = -18 + (n - 1) * 4.5 Add 18 to both side
60 + 18 = (n - 1) * 4.5
78 = (n - 1) * 4.5 Divide both sides by 4.5
78/4.5 = n - 1
17.3333 = n - 1 Add 1 to both sides.
18.3333 = n
Conclusion
It will that 18 1/3 or 18.33333 minutes to get the from -18 to 60 degrees.
slope intercept form
y=mx+b
where m is the slope and b is the y intercept
if we change from point slope form
y-y1 = m(x-x1)
we distribute
y-y1 = mx -x*x1
then add y1 to each side
y = mx -x*x1+y1
remember x and y are variables and should stay in the equation
m,x1,y1 are numbers from the problem
you may have to calculate the slope (m) from the formula
m = (y2-y1)/(x2-x1) from two points on the line
