To find the area, you will need to find the base (b). Using Pythagoras, you will need to find the length of AD:
C squared (hypotenuse) - b squared (other known side)= a squared (unknown side)
9 squared - 7 squared = a squared
81-49= a squared
32 =a squared
Square root of 32 = 5.6568542......
AD=5.7
You will then need to find DC:
C squared (hypotenuse) - b squared (other known side)= a squared (unknown side)
12 squared - 7 squared = a squared
144-49= a squared
95 =a squared
Square root of 95 = 9.7467943....
DC=9.7
AC = 9.7 + 5.7
=15.4
To find the area of ABC;
A = 1/2 bh
= 1/2 x 15.4 x 7
= 53.9
Therefore, the area of ABC = 53.9