Tell me how you solve these problems! i don't get it! : (

18 c

the answer is 7.5 square units


18 b

the answer is 10.5 square units


18 a

the answer is 12 square units


good luck

Lets get started :)

We know the area formula of a trapezium/trapezoid
Area =  (side 1 + side 2 )

In these examples, you need to note one thing very carefully, the graph is spaced with 2 units in the axes of x and y. It is not spaced with 1 unit 
Which means:  The axes begin as 2 , 4 , 6 ; - 2 , - 4 , - 6

18 ) c )
    ↓
Base 1 = 2 units
Base 2 = 4 + 4 = 8 units ( Only half the base length was shown, since it is the same below the x-axis, we multiply by 2 )
Height = 6 units

Apply the formula
Area =  x 6 x ( 8 + 2 )
         =  x 6 x 10
         = 30 units²

18 ) b )
    ↓
Base 1 = 2 + 2 = 4 units
Base 2 = 6 + 4 = 10 units 
Height = 4 + 2 = 6 units

Area =  x 6 x ( 10 + 4 )
         =  x 6 x 14
         = 42 units²

18 ) a )
    ↓
Base 1 = 2 + 2 = 4 units
Base 2 = 4 + 4 = 8 units
Height = 4 + 4 = 8 units

Area =  x 8 x ( 8 + 4 )
         =  x 8 x 12
         = 48 units²