Draw a triangle of Perimetre 30 cm and length of side in the ratio 1 is to 2 draw two more rectangles of the same perimeter with the length of sides in the ratio 2 is to 3 and 3:7 compute areas of all three rectangles

a triangle has 3 sides, and you only give one ratio. I guess it is isosceles. If so, then

1+2+2 = 5
30/5 = 6
so the sides are 6,12,12

for the rectangles,
2(2+3) = 10
30/10 = 3
so the dimensions are 6 by 9

Now you try the other rectangle