Answer
$a.$
$A=\left[\begin{array}{cc}
{6}&{9}\\
{3}&{12}\end{array}\right] , B=\left[\begin{array}{c}
{121.00}\\
{340.13}\end{array}\right]$
$b.$
$AB=\left[\begin{array}{c}{3787.17}\\{4444.56}\end{array}\right]$
Nikki's total tuition is ${{\$}} 3787.17$,
Joe's total tutotion is ${{\$}} 4444.56$
Work Step by Step
$a.$
$A=\left[\begin{array}{cc}
{6}&{9}\\
{3}&{12}\end{array}\right] , B=\left[\begin{array}{c}
{121.00}\\
{340.13}\end{array}\right]$
$b.$
$\begin{aligned}AB&=\left[\begin{array}{cc} {6}&{9}\\ {3}&{12}\end{array}\right]\left[\begin{array}{c}
{121.00}\\{340.13}\end{array}\right]\\ \\&=\left[\begin{array}{c}{6(121.00)+9(340.13)}\\{3(121.00)+12(340.13)}\end{array}\right] \\\\&=\left[\begin{array}{c}{3787.17}\\{4444.56}\end{array}\right]\end{aligned}$
Nikki's total tuition is ${{\$}} 3787.17$,
Joe's total tutotion is ${{\$}} 4444.56$
