Atour director collected $258 for 13 tour packages. tour package a costs $18 and tour package b cost $22. how many of each tour package were sold?

A + b = 13
22 a + 18 b = 258

a = 13 - b
22 * ( 13 - b ) + 18 b = 258
286 - 22 b + 18 b = 258
- 4 b = 258 - 286
- 4 b = - 28
b = ( - 28 ) : ( - 8 ) = 7
a = 13 - 7 = 6

6 tour packages a and 7 tour packages b were sold.