Question

Write and solve an equation to find the number.

The sum of a number and 9 is -2.

Answer 1

The first thing you need to do is to choose a variable (a letter) to represent the unknown number.
Which letter do you like to use as a variable?

Answer 2

B

Answer 3

now what do i do ?

Answer 4

Now we translate the sentence in the English language into a sentence in Math language.

Here is a table of English-Math vocabulary

English Math
a number means a variable (you chose B)
sum means +
is means =

Answer 5

Now we translate:

The sum of a number and 9 is -2.

B + 9 = -2

The equation is

B + 9 = -2

Answer 6

Now we need to solve the equation.
The rule in Algebra is that you can add the same number to both sides of an equation, and you can subtract the same number from both sides of an equation.

Answer 7

We want B by itself.
The number 9 is being added to B on the left side.
To get rid of the addition of 9, we need to subtract 9, but we must subtract from BOTH sides of the equation.