Subtract -47 from 18. This means:
18 - (-47)
When subtracting with a negative number you will do something called "Same-Add-Opposite." This means that you will keep the first number in the expression (in this case that is 18) the same. Then turn the subtraction sign into an addition sign. Finally you will take the "opposite" sign of the second number. When I say "opposite sign" I mean that if this number is positive it will become negative. If it was negative it will become positive.
Here is your expression after applying same - add - opposite:
18 + 47
65
Hope this helped!
~Just a girl in love with Shawn Mendes