Answer
The cost of the software is \$420.
The cost of the computer system is \$1680.
Work Step by Step
Let the cost of the software be $s$.
The cost if the computer system be $4s$.
$s+4s=2100$ $\longrightarrow$combine like terms
$5s=2100$ $\longrightarrow$multiplication property
$5s\div5=2100\div5$ $\longrightarrow$divide
$s=420$
$4s=4\times420=1680$
