Tim bought a certain number of bags of chips that each cost $1.05. Write an expression to show the total cost.

x is the number of bags of chips

1.05x means "1.05 times x". You could write 1.05*x or omit the multiplication symbol all together.

For example, if he bought x = 100 bags then he would spend 1.05*x = 1.05*100 = 105 dollars.