Step-by-step explanation:
Six friends order lunch.
each person orders one sandwich and one cookie.
Let x be the cost of 1 sandwich and y be the cost of 1 cookie
The expression for the cost of each person is
1 sandwich + 1 cookie
1x + 1y
To find the expression for the total cost of 6 persons, multiply the cost of 1 person by 6
So expression becomes 6(1x+1y) = 6x + 6y
