Evaluate the expressioncan someone please help me with this question? thanks in advance http://img585.imageshack.us/img585/8984/mathh.jpg

You should notice that you may find the area of shaded
region subtracting from the area of large right angle triangle, the area of small right
angle triangle.

You need to evaluate the area of large
right angle triangle considering the legs x+4 and x+6 such
that:

You
need to evaluate the area of small right angle triangle such
that:

You
may now evaluate the area of shaded region, hence, you need to subtract a from A such
that:

Notice that you may factor out   such
that:

4)

- a = 5(x+4)

You need to evaluate the area of shaded
region for x = 12 in such that:

= 80

Hence, evaluating the area of
shaded region in terms of x yields   and evaluating the area if
12A - a = 80 .