slope intercept form:
y= mx+b
Where:
m= slope
b= y-intercept
total pounds: y
number of weeks: x
the total number of pounds must be equal to the pounds already collected (100) plus the product of the number of weeks (x) and the number of pounds collected per week (25)
y= 100+25x
To collect 400 pounds, replace y by 400 and solve for x ( weeks)
400 = 100+25x
400-100= 25x
300=25x
300/25 = x
12 = x
12 weeks to collect 400 pounds