Solve {|l|l}hlinetext{7.}&{9.9-9}hlinetext{8.}&{9.9-0.9}

$$\left. \begin{array} { | l | l } \hline \text { 7. } & { 9.9 - 9 } \\ \hline \text { 8. } & { 9.9 - 0.9 } \end{array} \right.$$

Calculate Determinant

$$55.8$$

Steps Using Diagonal Rule

Subtract 9 from 9.9 to get 0.9.

$$det(\left(\begin{matrix}7&0.9\\8&9.9-0.9\end{matrix}\right))$$

Subtract 0.9 from 9.9 to get 9.

$$det(\left(\begin{matrix}7&0.9\\8&9\end{matrix}\right))$$

For the 2\times 2 matrix \left(\begin{matrix}a&b\\c&d\end{matrix}\right), the determinant is ad-bc.

$$7\times 9-0.9\times 8$$

Multiply 7 times 9.

$$63-0.9\times 8$$

Multiply 0.9 times 8.

$$63-7.2$$

Subtract 7.2 from 63.

$$55.8$$

Evaluate

$$\left(\begin{matrix}7&0.9\\8&9\end{matrix}\right)$$