Question

10 more than a number c is 3.

Answer 1

10 more than a number c: c + 10

is 3:

c + 10 = 3       subtract 10 from both sides

c + 10 - 10 = 3 - 10

c = -7

Answer 2

Is the question what c is?
if so just subtract 3 from 10
3-10 = -7

therefore c = -7
hope that helps :)