Line y = kx + b passes through points A (2: 7) and B (-1: -2) Find the values of k and b

Substitute the straight line y = kx + b into the equation instead of the value of the variable x = 2, and instead of y = 7 and instead of x = -1 and instead of y = -2. We get the system of equations:
{7 = k * 2 + b,
{-2 = k * (-1) + b;
{7 = k * 2 + b,
{-2 = – k + b (we express the variable k from this equation);
{7 = k * 2 + b,
{k = 2 + b (substitute in the first equation);
{7 = (2 + b) * 2 + b,
{k = 2 + b;
{7 = 4 + b * 2 + b,
{k = 2 + b;
{7 – 4 = b * 3,
{k = 2 + b;
{3 = b * 3,
{k = 2 + b;
{1 = b,
{k = 2 + b;
{1 = b,
{k = 2 + 1;
{1 = b,
{k = 2 + 1;
{1 = b,
{k = 3.
Answer: y = 3x + 1.