Question 379625
Let B be the cost of the book, P the cost of the pen.
1.{{{B=2P}}}
2.{{{P+B=48}}}
Substitute using eq. 1,
{{{P+2P=48}}}
{{{3P=48}}}
{{{highlight(P=16)}}}
Then from eq. 1,
{{{B=2(16)}}}
{{{highlight(B=32)}}}