Solve for X: Rectangle with Area 78 cm² and Width 3 cm

We know that the area of a rectangle is equal to its length multiplied by its width.

We begin by writing an equation with the available data.

$78=3\times(x+7)$

We then use the distributive property to solve the equation.

That is, we multiply each of the terms inside of the parentheses by 3:

$78=3\times x+3\times7$

$78=3x+21$

We move 21 to the other side and use the appropriate sign:

$78-21=3x$

$57=3x$

Lastly we divide both sides by 3:

$\frac{57}{3}=\frac{3x}{3}$

$x=19$