Can you tell me it in a easier way?

Dear student
Consider scalene triangle ABC

area of triangle ABC = area of triangle ABE + area of triangle CBE

area of triangle ABC = (y × h)/2 + (x × h)/2

area of triangle ABC = (y × h + x × h)/2

area of triangle ABC = h ×(y + x)/2

Notice that y + x is the length of the base of triangle ABC.

Thus, it is ok to say that y + x = b

Therefore, area of triangle ABC = $\frac{hb}{2}$
Regards