Final answer:
To find the error in the equation -10/21 = -2/3a, we need to solve for 'a' and check if the equation holds true. The correct value of 'a' is 5/7, not -10/14.
Step-by-step explanation:
To find the error in the equation -10/21 = -2/3a, we need to solve for 'a' and check if the equation holds true.
Multiplying both sides of the equation by 21 gives: -10 = -14a
Dividing both sides of the equation by -14 gives: a = 10/14 = 5/7
So, the error in the equation is that the correct value of 'a' is 5/7, not -10/14.