Respuesta :

madethisfortwitch1

Answer:

210

Step-by-step explanation:

The perimeter is the sum of all sides

which means that

3a-1+4a+1+3a=70

combine like terms

10a=70

a=7

Now we need to work out the area

which is bh*.5

which means that we have

(21-1)*21*.5

compute this and get 210

Lifeliner

Answer:

210cm²

Step-by-step explanation:

3x-1 + 4x+1 + 3x =

10x

70 ÷ 10 = 7

x = 7

area =  1/2 (b × h)

3x-1 = 20

3x = 21                                     x=7

20 × 21 = 420

420 ÷ 2 =210