The boat sailed 30 kilometers along the river, 13 kilometers against the current, spending 1

The boat sailed 30 kilometers along the river, 13 kilometers against the current, spending 1 hour and 30 minutes for the whole journey. What is the boat’s own speed if the speed of the river is 2 km / hour.

Let x be the boat’s own speed;
(x + 2) – speed along the river;
(x – 2) – speed upstream of the river;
Let’s make the equation:
30 / (x + 2) + 13 / (x – 2) = 1.5;
30 (x – 2) + 13 (x + 2) = 1.5 (x – 2) (x + 2);
30x – 60 + 13x + 26 + 1.5x ^ 2 – 1.5 4;
1.5 x ^ 2 – 43x + 28 = 0;
Multiply both sides by 2;
3x ^ 2 – 86x + 56 = 0;
D = 82;
x1 = (86 + 82) / 6 = 28;
x2 = (86 – 82) / 6 = -2/3 – does not satisfy the conditions of the problem;
Answer: The boat’s own speed is 28 km / h.