Chairs are on sale for $7 and tables are on sale for $40. If a store sold a totally of 30 of these items and collected $507, how much of each were sold?

Answer:
21 chairs and 9 tables
Step-by-step explanation:
c=chair
t=table
c + t = 30
7c + 40t = 507
I am going to solve this using elimination by multiplying the top equation by -7
-7c - 7t = -210
7c + 40t = 507
subtract downwards
33t = 297
t= 9
there are 9 tables
c + 9 = 30
c= 21
there are 21 chairs