When we simplify algebraic expressions we combine the coefficients of like terms.
Like terms are terms with matching letters.
3a, 4a and a are like terms.
2b, -b, -5b are like terms.
2b and b2 are not like terms.
3b and 3 are not like terms.
3b, 5c and -2 are not like terms.
Simplify -4 + 3b + 4b - a + 2b + 6a + 3
Look at the coefficients of all the as...... -a + 6a which are -1a + 6a
Combine them to get -1 + 6 = 5
So we get 5a
Look at the coefficients of all the bs...... 3b + 4b + 2b which are 3b + 4b +2b
Combine them to get 3 + 4 +2 = 9
So we get 9b
Combine the numbers which are -4 + 3 = -1
The answer is 5a + 9b - 1