# How do you write as a mathematical expression and solve: The sum of a number and 8 times the number is 45?

$x + 8 x = 45 , x = 6$

#### Explanation:

Like this:

"The sum of a number (which I'll call $x$)":

$x +$

"and eight times a number":

$x + 8 x$

"is 45":

$x + 8 x = 45$

and now we solve, first by adding the x-terms together:

$9 x = 45$

then divide both sides by 9:

$\frac{9 x}{9} = \frac{45}{9}$

$\frac{\cancel{9} x}{\cancel{9}} = \frac{45}{9} = \frac{6 \times 9}{9} = \frac{6 \times \cancel{9}}{\cancel{9}} = 6$