Anita's cell phone plan costs R100 per month. It includes 50 free peak time SMS and 100 free off-peak time SMS. Peak time SMS cost R0.85 each and off-peak time SMS cost R0.25 each. In a month, Anita s

The cost per peak time SMS is 85 cents, which is R0.85.
Anita sent 45 SMS during peak time.

$$\text{Peak time SMS cost} = 45 \times \text{R}0.85 = \text{R}38.25$$

The cost per off-peak time SMS is 25 cents, which is R0.25.
Anita sent 105 SMS during off-peak time.

$$\text{Off-peak time SMS cost} = 105 \times \text{R}0.25 = \text{R}26.25$$

The total monthly bill is the sum of the monthly contract cost, peak time SMS cost, and off-peak time SMS cost.

$$\text{Total monthly bill} = \text{R}100 + \text{R}38.25 + \text{R}26.25$$ $$\text{Total monthly bill} = \text{R}164.50$$

The total monthly bill will be $\text{R}164.50$.