x = rice demand in kg

m = consumer income in $

p = price of rice per kg

Step #1

m = 4800

p = 120

x = ?

x = 15 + m(10p)^-1

x = 15 + (4800)*(10(120))^-1

x = 15 + (4800)*(1200)^-1

x = 15 + (4800)*(1/1200)

x = 15 + 4

x = 19

Solution:

For m = 4800 and p = 120 there is consumer demand for 19kg of rice

Hints to finish the problem:

1. Although it take a minute longer, it's possible to achieve a high level of accuracy by clearly stating the values you have, and the values you want.

2. Pay careful attention to units. Units should definitely be given in your answer

3. The problem asks you to calculate the (in plain terms) difference between p = 120 and p = 100. Step #2 involves solving for p = 100

4. The final results are given by specifically comparing the x values for p = 120 and p = 100