1-14, You're just dividing. Like #1, -14÷2=-7 (negative fourteen divided by two, equals negative seven). A positive and a positive make a positive, a negative and a positive make a negative, a negative and a negative, make a positive. The word problems your also dividing, for example, #15, -40÷4=-10. Use the numbers that are given to you.
X-7=8
Add 7 to both sides so you can isolate the variable
x=15
60-12-18-2-8=20
=48-18-2-8
=30-2-8
=28-8
=20
So, 20 students don't take either of these subjects.