You would be right with 26 because the absolute value of -30 is 30 then you subtract 56-30 and get 26 which is the remaining temp you need to get to 56.
You have to find the discriminat b^2 -4ac
If it is > 0, the function has two real solutions
if it is = 0, the function has one real solution
if it is <0, the function has no real solution
6^2 - 4(7)(3) = 36 - 84 = - 48
Answer c. no solution
ANSWER
The radius is 8
EXPLANATION
We were given,

We rewrite the above equation to obtain,

We now add half the square of the coefficient of

to both sides of the equation to get,

We now got two perfect squares on the left hand side of the equation,



By comparing to the general formula of the circle,

We can see that the radius is 8.