First, read and re-read a word (story) problem until you understand it and can put it into your own words.
Here's mine: There are 5-seat tables and 6-seat tables, with a total of 26 tables. There are 136 seats. How many of each table are there?
[note: I assumed equalities, but this problem could have involved inequalities.]
x = number of 5-seat tables
y = number of 6-seat tables
(note: fire code limits are given in terms of "customers," not people)
"136 customers" means 5x + 6y = 136 [eq1]
"26 tables " means x + y = 26 [eq2]
Use either substitution or elimination (let's use substitution):
y = 26-x [from eq2]
5x + 6(26-x) = 136 [substitute for x in eq2]
5x + 156 - 6x = 136 [distribute]
-x = -20 [collect terms; subtract 156 from both sides]
x = 20 [multiply both sides by (-20)]
(20) + y = 26 [from eq2; you could use either eq1 or eq2 here]
y = 6
Does 5(20) + 6(6) = 136 ?
100 + 36 = 136 ?
136 = 136 ?yes