Carlos solved the equation below for x. His solution is x = 5. What mistake did Carlos make and how could he have verified his solution to know for certain that his answer is correct?
2x - 9 = 19
2x = 10
x = 5
Carlos made a mistake when solving the equation. On the third line, the equation should be x = 10/2, not x = 5. Therefore, Carlos made an error in dividing 10 by 2.
To verify his solution, Carlos could substitute x = 5 back into the original equation and see if it holds true. Substituting x = 5 into 2x - 9 = 19 would give 2(5) - 9 = 10 - 9 = 1, which is not equal to 19. Thus, Carlos can determine that his solution is incorrect.