#### Answer

Area is decreased by 16%.

#### Work Step by Step

Lets take the initial base of a rectangle be b
and the height be h
Base is increased by 20% of b
therefore final Base = 1.2 b
The altitude is decreased by 30 % of h
Final altitude =0.7 h
The area of rectangle whose base has length b and altitude has length h is given by A = bh
Initial area of rectangle = bh
Final area of rectangle = (1.2b) * (0.7h)
= 0.84bh
Increase in area of rectangle in percentage = $\frac{final area - initial area}{initial area}$ * 100
=$\frac{0.84bh - bh}{bh}$ * 100
=$\frac{-0.16bh}{bh}$ * 100
= -0.16 * 100 = -16%
therefore 16% area is decreased