Find b if it is known that the graph of the function y = 3x + b passes through the point A (15; 40).

If the graph of the function y = 3x + b passes through point A with coordinates (15; 40), then substituting the values x = 15 and y = 40 into the equation of this function, we should get the correct equality:

40 = 3 * 15 + b.

Therefore, it is necessary to find at what value of b this equality holds.

We solve the resulting equation and find what is equal to.

40 = 45 + b.

Subtracting 45 from both sides of the equation, we get:

40 – 45 = 45 + b – 45;

b = -5.

Therefore, the graph of the function y = 3x + b passes through point A with coordinates (15; 40) at b = -5.

Answer: b = -5.