3•a=781-157

To solve the equation \(3a = 781 - 157\), first, calculate the right side:

\[ 781 - 157 = 624 \]

Now we have:

\[ 3a = 624 \]

Next, divide both sides by 3 to find \(a\):

\[ a = \frac{624}{3} = 208 \]

So, the solution is:

\[ a = 208 \]