## Algebra 1

Use mental math. What number can be added to 4 to equal 13? $9+4=13$ You can use a table to find the value. $\underline{x}\ \ \ \ \underline{x+4}$ $1\ \ \ \ \ \ \ \ 5$ $2\ \ \ \ \ \ \ \ 6$ $3\ \ \ \ \ \ \ \ 7$ $4\ \ \ \ \ \ \ \ 8$ $5\ \ \ \ \ \ \ \ 9$ $6\ \ \ \ \ \ \ \ 10$ $7\ \ \ \ \ \ \ \ 11$ $8\ \ \ \ \ \ \ \ 12$ $9\ \ \ \ \ \ \ \ 13\longrightarrow$ the solution is 9