Final answer:
The expression 6a-7b+8 contains 'a' and 'b' as variables, with 6 and -7 as their respective coefficients. The number 8 is a constant.
Step-by-step explanation:
The variables in the expression 6a-7b+8 are ‘a’ and ‘b’. These are called variables because they represent unknown values that can change or vary. The numbers 6 and -7 are the coefficients of the variables, indicating how many times each variable is multiplied. The number 8 is a constant, which is a fixed value that does not contain a variable. In algebra, identifying variables is a fundamental skill as it helps in understanding how to manipulate and solve expressions and equations.