[tex](1)... ducem\; \^{i}n\u{a}l\c{t}imea\;trapezului\; din\; B\;\\
pe\;baza mare\;;\\
(2)...\;exprim\u{a}m\;inaltimea\; h\; al\; trapezului\;\\
adic\u{a}:\\
(7+5)/2\,*\,h=24\;\Rightarrow\;6h=24\;deci\;h=24/6=4cm\;;\\
(3)...A_\Delta{ABC}=A_{ABCD}-A_{ACD}=\\
=24\,-\,(7*4)/2= 24-28:2=24-14=10cm^2
[/tex]