Mikaela spent 35 + 5 = <<35+5=40>>40 hours in the second month.
So, she tutored a total of 35 + 40 = <<35+40=75>>75 hours for the first two months.
Thus, her total earning was 75 x $10 = $<<75*10=750>>750.
And, her total expenses was 4/5 x $750 = $<<4/5*750=600>>600.
Therefore, she saved an amount of $750 - $600 = $<<750-600=150>>150.
#### 150