Since, the point (x = 3, y = 4) lies on the equation 3y = ax + 7, the equation will be satisfied by this point.
Now, put x = 3 and y = 4 in given equation 3y = ax + 7, we get,
⇒3(4)=a(3)+7
⇒12=3a+7
⇒3a=12−7
⇒3a=5
∴a=53
Hence, the value of a is 53.