Question

A number increased by nine is fifteen

Answer 1

step 1. use x to represent “a number”. in word problems like so, key words like “increased by” and “is” tell you how to set up the equation. “increased by” is the same thing as adding one number to another. “is” is the same thing as an equal sign. you would set this up like so....
x+9=15
step 2. if asked to solve for the number (x), you must isolate it (x) on one side of the = sign. to do this you would undo it by using the reverse operation. the reverse of addition is subtraction and vice versa (same thing goes for multiplication and division).in this problem, subtract 9 from both sides. whatever you do to one side you MUST do to the other.
x-9=15-9
step 3. now that x is all alone you can sole for it by doing the math on the other side of the equation. so, 15-9, which equals 6. therefore your answer would be...
x=6
step 4. you should then check your work by simply plugging the number you got for x into the original equation.
(6)+9=15
if both sides of the equation are equal, you did everything correctly and can move on!
15=15 (correct!)
hope this helps (:

Answer 2

We will represent "a number" as
`n`. This number,
`n`, is being "increased by nine," which means that 9 is added to this number. Since "is" means "equivalent" we can say:

`n + 9 = 15`

`\boxed{n = 6}`

Our number is 6.