Let the total number of points be \(x\).

15% of \(x\) is 45, so:

\(0.15x = 45\).

Divide both sides by 0.15:

\(x = \dfrac{45}{0.15} = 300\).

Answer: 300

Find 20% of 40:

\(20\% = 0.20\), so \(0.20 \times 40 = 8\).

The discount is \($8\).

Sale price = original price − discount:

\(40 - 8 = 32\).

Answer: 32

Correct answers = 80% of 50.

\(80\% = 0.80\), so \(0.80 \times 50 = 40\).

She answered 40 questions correctly.

Answer: 40

Let the original price be \(x\).

A 25% discount means you pay 75% of the original price:

\(0.75x = 75\).

Divide both sides by 0.75:

\(x = \dfrac{75}{0.75} = 100\).

Answer: 100

Let the number be \(x\).

25% of \(x\) is 30, so:

\(0.25x = 30\).

Divide both sides by 0.25:

\(x = \dfrac{30}{0.25} = 120\).

Answer: 120

Let the original amount be \(x\).

Decreasing by 15% means 85% is left:

\(0.85x = 85\).

Divide both sides by 0.85:

\(x = \dfrac{85}{0.85} = 100\).

Answer: 100

Tip = 15% of 120.

\(15\% = 0.15\), so tip = \(0.15 \times 120 = 18\).

Total cost = bill + tip:

\(120 + 18 = 138\).

Answer: 138

Let the original profit be \(x\).

After a 10% increase, the new profit is 110% of the original:

\(1.10x = 55000\).

Divide both sides by 1.10:

\(x = \dfrac{55000}{1.10} = 50000\).

Answer: 50000