Question 883679
{{{a^2}}}+{{{b^2}}}={{{c^2}}}
You're given one leg and the hypotenuse.
{{{4^2}}}+{{{b^2}}}={{{5^2}}}
16+{{{b^2}}}=25
Subtract 16 from each side
{{{b^2}}}=9
Take the square root
b = 3
.
Your sides are 4 and 3.  Multiply to get the area.
4*3=12