Question

half the sum of 12 and x2 decreased by one-third x

Answer 1

The sum of 12 and x squared is

$12+x^2$

Half that sum is

$\dfrac{1}{2}(12+x^2)$

If we decrease this quantity by 1/3 x we have

$\dfrac{1}{2}(12+x^2) - \dfrac{1}{3}x$