Sergio's expression is incorrect because he can not simplify 3-6x and Leon's expression is incorrect because he did not multiply 3 by -1.
Here, given expression, 9 - (3 - 6x)
After simplifying this we get the following steps,
Step 1) 9 - (3 - 6x) = 9 - 3 +6x ( by removing parenthesis ) (1)
Step 2) 9 - (3 - 6x) = 6 + 6x
Step 3) 9 - (3 - 6x) = 6(1 + x) ( because 6 is common in both term of right side)
Since, when Sergio simplified it he wrote 9−(-3x), which is not matching to the above steps. that, is he is incorrect, because in his explanation he wrote -3x after simplifying 3-6x which can not be solved.
Moreover, the expression of Leon is also not matching to any of the above steps,
Thus he is also incorrect because after removing parenthesis he did not multiply 3 by -1 .
Leon : correct because he distributed correctly
Given expression is:
9 - (3 - 6x)
We have to find the equivalent expression
Use the distributive property,
a(b + c) = ab + bc
Therefore, from given expression,
Combine the constants, 9 - 3 = 6
Thus the equivalent expression is 6 + 6x
correct me if i am wrong.