250 = 167.93 + x
[She needs $250, she has $167.93, and she needs x more. x represents the amount of money she still needs in order to get 250]
250 = 167.93 + x Subtract 167.93 on both sides
250 - 167.93 = 167.93 + x - 167.93
250 - 167.93 = x
82.07 = x
She needs $82.07 more
Or you could have done:
250 - 167.93 = 82.07
