Aspecies of extremely rare, deep water fish is going extinct. if there are a total 821 of this type of fish and there are 15% fewer fish each month how many will there be in half a year?

Can someone pls ! pls answer all. no explanation needed..

The volume of gas a balloon can hold varies directly as the cube of its radius. imagine a balloon with a radius of 3 inches can hold 81 cubic inches of gas. how many cubic inches of gas must be released to reduce the radius down to 2 inches?

If 2(a^2+b^2)=(a+b)^2 then, > a+b=0, > ab=0, > a=b, > 2a=b