The answer is b = 50.
The general form of quadratic equation is
ax² + bx + c = 0.
To write the equation 0.3x² + 5x - 7 = 0 in standard form, you must get rid of decimals. To do that, multiply the equation by 10:
10 * (0.3x² + 5x - 7) = 10 * 0
10 * 0.3x² + 10 * 5x - 10 * 7 = 0
3x² + 50x - 70 = 0
Now compare this equation with the general formula:
ax² + bx + c = 0
3x² + 50x - 70 = 0
Therefore, b = 50.