Yes I think so I could be wrong but I think the answer is yes it is proportional
7(a^2+b)-4(a^2+b)
7(a^2)+7b-4(a^2)-4b
7a^2-4a^2+7b-4b
(7-4)a^2+(7-4)b
3a^2+3b
If 150g of fertilizer can cover 6 sq m of land then, 25 g of fertilizer can cover 1 sq m of land;
a)
For 13 sq m of land we need 25g*13
325g
b)
850g/25g=amount of land
34 sq m
