Given:
Total amount of Mingfa and her sister = $130
If Mingfa amount increased by $10, then the new amount is equal to three times of as much money as her sister.
To find:
How much money does Mingfa actually have?
Solution:
Let, Mingfa have $x and her sister has $y initially. Then,
...(i)
If Mingfa amount increased by $10, then the new amount is equal to three times of as much money as her sister.
...(ii)
Substitute the value of x from (ii) in (i).
Divide both sides by 4.
Putting in (i), we get
Therefore, Mingfa have $95.