First add all Janet's grade for the first semester of college: 90 + 80 + 70 + 100 = <<90+80+70+100=340>>340
Then divide that number by 4 to find her average grade: 340 / 4 = <<340/4=85>>85
Then subtract her semester 2 average to find the difference: 85 - 82 = <<85-82=3>>3
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