Careful: 增加了三倍 means 'increased by 3x' (final = 4x original), while 增加到三倍 means 'increased to 3x' (final = 3x). 一倍 famously means 'twice as much', not '1x'.
grammar
Pattern: A 是 B 的三倍 = 'A is three times B'. Always uses 的 not 倍 of directly: 三倍工资 works as a modifier, but for comparison you need 是...的三倍.
