How do you write, in algebraic form, "one half a number decreased by 4 is equal to 21"?

Question

3260 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-10-18T01:02:49

See a solution process below:

First, let's call "a number": #n#

Then, "one-half of a number" can be written as:

#(1/2 * n)# or #n/2#

To "decrease by 3" means to subtract #3# from this number which let's us write:

#n/2 - 3#

In this expression the word "is" means it "is equal to" so we can now add:

#n/2 - 3 =#

We are told it is equal to "21" so we can finish writing the expression as:

#n/2 - 3 = 21#