Question 170991
By Pyth Theorem:
{{{AC^2=AB^2+BC^2}}}
{{{AC^2=9^2+12^2}}}
{{{AC^2=81+144}}}
{{{AC=sqrt(225)}}}
{{{highlight(AC=15cm)}}}, ANSWER, sorry for the typo (adjusted)
.
Thank you,
Jojo