I guess you mean all upper quotes
3A+ 4B-2C-4A+5B-1C = (3*2) + [4*(-1) ] - (2*4) - (4*2) + [ 5*(-1) ] - (1*4)
= 6 + (-4) - 8 -8 + (-5) - 4
= 6 - 4 - 8 - 8 - 5 - 4
= 6 - 29
= -23
remember that
+ve * +ve = +ve
+ve * -ve = -ve
-ve * -ve = +ve
see this page for precedence of operations
order of performing mathematical operations
first you collect "like terms", not sure if thats a term you have used but it means adding up whats "like" before subing numbers in so
3A + 4B - 2C - 4A +5B - C becomes
-1A +9B -3C ( as you have added all the A's together and so on.)
then you sub in the numbers so,
-1(2) + 9(-1) -3(4) = -2-9-12 = -23