The given equation is $y=\frac{1}{2}(3x+7)$.
Simplifying the equation we get
$2y-3x-7=0$ 
Rewriting the equation in standard form ax + by + c = 0 we get
$-3x+2y-7=0$
$\therefore$ On comparing the above equation with standard form ax + by +c = 0, we get the values of a, b and c is -3, 2 and -7 respectively.
But the equation can also be written as,
$3x-2y+7=0$
(By multiplying both the sides by (-1))
$\therefore$ On comparing the above equation with standard form ax + by +c = 0, we get the value of a, b and c is +3, -2 and +7 respectively.