Let n be the number.

It looks like your problem statement is saying

3n = 2n-7 (the difference of twice the number and 7)

n = -7 (after we subtract 2n from both sides)

We could also write "the difference of twice the number and 7" as 7-2n. Then,

3n = 7 - 2n

5n = 7

n = 7/5 = 1.4

The difference of twice the number and 7 would be 7 - 2.8 = 4.2. English is a little vague on the precise meaning of "the difference of 2.8 and 7". Is it +4.2, or -4.2? Likewise, is "the difference of -14 and 7" equal to -21, or to +21?

It looks like your problem statement is saying

3n = 2n-7 (the difference of twice the number and 7)

n = -7 (after we subtract 2n from both sides)

We could also write "the difference of twice the number and 7" as 7-2n. Then,

3n = 7 - 2n

5n = 7

n = 7/5 = 1.4

The difference of twice the number and 7 would be 7 - 2.8 = 4.2. English is a little vague on the precise meaning of "the difference of 2.8 and 7". Is it +4.2, or -4.2? Likewise, is "the difference of -14 and 7" equal to -21, or to +21?