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rafael is charging his tablet. as the tablet charges, the amount of battery charge increases at a constant rate. the graph below shows the linear relationship between the time x (in hours) since the tablet began charging and the amount of battery charge y (as a percentage).
write a linear equation to represent the relationship between x and y.

Explanation:

Step1: Identify y-intercept ($b$)

The y-intercept is the value of $y$ when $x=0$. From the graph, when $x=0$, $y=30$, so $b=30$.

Step2: Calculate slope ($m$)

Slope is $\frac{\Delta y}{\Delta x}$. Use points $(0,30)$ and $(4,70)$:
$\Delta y = 70-30=40$, $\Delta x=4-0=4$
$m=\frac{40}{4}=10$

Step3: Write linear equation

Use slope-intercept form $y=mx+b$:
Substitute $m=10$ and $b=30$

Answer:

$y=10x+30$