Write each subtraction equation as an addition equation.

1. \(5 - 8 = a\)
2. \(\text-30 - 20 = p\)
3. \(7-(\text-10)=x\)
4. \(\text-12 - (\text-15)=z\)

Find each difference. If you get stuck, consider drawing a number line diagram.

1. \(9 - 4\)

2. \(4 - 9\)

3. \(9 - (\text-4)\)

4. \(\text-9 - (\text-4)\)

5. \(\text-9 - 4\)

6. \(4 - (\text-9)\)

7. \(\text-4 - (\text-9)\)

A restaurant bill is \$59, and you pay \$72. What percentage gratuity did you pay?

Find the solution to each equation mentally.

1. \(30+a=40\)
2. \(500+b=200\)
3. \(\text-1+c=\text-2\)
4. \(d+3,\!567=0\)

One kilogram is 2.2 pounds. Complete the tables. What is the interpretation of the constant of proportionality in each case?