hey!!
first of all divide it in two parts.
one rectangle of length given 7 and breadth 3 and one triangle of height 3 and base 7.
therefore total area of the shape = ( l × b ) + ( 1/2 × b × h )
= ( 7 × 3 ) + ( 1/2 × 7 × 3 )
= 21 + ( 3.5 × 3 )
= 21 + 10.5
= 31.5 unit²
cheers!!!