Answer: 14.2 weeks
Explanation:
We can set up a linear equation to find the least amount of weeks to save the certain amount. First, let's define variables:
x is weeks, which is the independent variable, and y is money, which is a variable dependent on the time (weeks).
Because he has 15$ given previously, that isn't going to change regardless of time, so it's a constant value.
So, if Charles works 0 weeks, he has 15 dollars regardless. But, if he were to work two weeks, he has 15 dollars and 10 dollars saved throughout the span of the weeks, so he has 25 dollars total.
Given this information, we can formulate a proper equation now to represent his saving:
y = 5x + 15
To find the least amount of weeks to save 136 dollars, substitute y with 136 and solve for that.
136 - 15 = 5x
121 - 5x
14.2 = x
Therefore, the least time it will take him to save 136$ is 14.2 weeks.