(a) Betty’s expression:
Cost of guest = 10 × x + 10 × x + 10 × x
          = 10x + 10x + 10x
cost of the venue = 80
Total cost = 10x + 10x + 10x + 80
(b) Dawnie’s expression:
Cost of the location  = $80
Number of guests = x + x + x
Cost of all guests = $10(x + x + x)
Total cost = 10(x + x + x) + 80
(c) Joan’s expression:
Cost of the location = 80
Cost of guest = 10 × x + 10 × x + 10 × x
          = 10x + 10x + 10x
          = x(10 + 10 + 10)   ⇒  After factoring out x. Â
Total cost = x(10 + 10 + 10) + 80