Chapter 3.CR, Problem 40CR

Recall that addition problems like $3478+521$ can be written and computed using expanded notation as shown here, and answer the questions that follow.

$\begin{array}{l}3\cdot {10}^3+4\cdot {10}^2+7\cdot 10+8\\ +5\cdot {10}^2+2\cdot 10+1\\ \overline{3\cdot {10}^3+9\cdot {10}^2+9\cdot 10+9}\end{array}$

a. Write a corresponding addition algebra problem (use $x$ for $10$) and find the answer.

b. Write a subtraction problem and the corresponding algebra problem and find the answer.

c. Write a multiplication problem and the corresponding algebra problem and compute the answer.