12(a + b) + 4(2a + b) − 6(a + 3b)
simplify the expression

=12(a + b) + 4(2a + b) − 6(a + 3b)
=12a + 12b + 8a + 4b - 6a - 18b

Now, Try to put every a's together & every b's together,
= (12a+8a-6a) + (12b+4b-18b)
= 14a - 2b

In short, Your Answer would be 14a - 2b

Hope this helps!

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