The answer is quintic binomial.
It is quintic because its highest power is 5. Quartic would mean its highest power is 4.
It is a binomial because the two terms are -4x^5 and -6x^3. Terms are separated by + or - signs.
You just have to go 7x28=[7x20]+[7x8]=196
Write an equation, calling the number x:
3x=2(x+4)
3x=2x+8
x=8
However, 8 is not a perfect square, which was required in the problem, so there are no solutions.
I believe the answer is 2.02