If Robert buys a candy bar for 78 cents, how much change does he get back from a one-dollar bill?

Hint:In this question, we are given a mathematical statement, to solve it we have to convert it into a mathematical equation; we do it with the help of algebra. The combination of both numerical values and alphabets forms a mathematical operation called the algebraic expression. After converting this equation into the algebraic expression, we can solve it to find the value of x.

Complete step by step answer:
Robert buys candy for 78 cents and he pays one dollar.

We know that one dollar is equal to 100 cents, so the shop keeper will keep 78 cents and returns the remaining money to him, so the equation can be formed as –
78+x = 100

So, the change that Robert will receive, x = 100-78 = 22 cents.

Hence, if Robert buys a candy bar for 78 cents and pays a one-dollar bill, he will get back a change of 22 cents.

Note:In simple words, in algebra we use alphabets to represent numbers to get a more generalized expression or formula or equation, they also involve mathematical operations. There are different units for measuring the same quantity because of the different applications of the quantity. For example, daily life involves a large amount of money for big transactions like buying a car but small money for small transactions like buying candy. One unit of quantity can be easily converted into another by knowing the relation between the two.