Amanda has 7 - 3 = <<7-3=4>>4 candy bars.
Amandy gives her sister 4 x 3 = <<4*3=12>>12 candy bars.
She has 30 - 12 = <<30-12=18>>18 candy bars remaining.
In total she keeps 18 + 4 = <<18+4=22>>22 candy bars.
#### 22