The difference of a number p and -9 is 12. What is the number?

1 Answer
smendyka
Jan 13, 2017

#p = 3#

Explanation:

We can write the equation from this word problem by looking at each part of the question.

"The difference of" is saying to subtract what follows.

"a number #p# and #-9# means we have to subtract #color(red)(-9)# from #color(blue)(p)#. Remember, we need to subtract a minus 9 or negative nine - so minus a negative number.

We can write this as #color(blue)(p) - color(red)(-9)#

In math the word "is" means equal to or #=#.

And the expression is equal to #12#.

Writing the entire problem out gives:

#color(blue)(p) - color(red)(-9) = 12#

We can rewrite as:

#color(blue)(p) + color(red)(9) = 12#

Solving:

#color(blue)(p) + color(red)(9) - 9 = 12 - 9#

#color(blue)(p) + 0 = 3#

#p = 3#

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