What is the solution of (15-5x<0)?

Correct answer: x>3

The governing rule is that multiplying or dividing an inequality by a negative number reverses its inequality sign. Begin with 15−5x<0. Subtract 15 from both sides: −5x<−15. Now divide both sides by −5; because the divisor is negative, the sign changes from < to >, giving x>3. Thus option A is correct. A quick check supports it: taking x=4 gives 15−20=−5<0, while x=2 gives 15−10=5, which is not less than zero. Options B, C, and D either reverse the direction incorrectly or include the boundary value 3, although 15−5(3)=0 and the original inequality is strict.