Answer
The cost of a pen is $\$1.8$ and a pad is $\$2$.
Work Step by Step
Let us assume the cost of one pen is $ x $ and one pad is $ y $. From the given data:
$10x+12y=42$ (I)
$5x+10y=29$ (II)
And subtract (I) from 2*(II) as:
$\begin{align}
& 10x+20y-10x-12y=58-42 \\
& 8y=16 \\
& y=2
\end{align}$
And to get the value of $ x $ put $ y=2$ in (I) as:
$\begin{align}
& 10x+12\left( 2 \right)=42 \\
& 10x=42-24 \\
& 10x=18 \\
& x=1.8
\end{align}$
Thus, the cost of a pen is $\$1.8$ and a pad is $\$2$.
