Step-by-step explanation:
1. x² = V12²+16²
= V144+256
= V400
x² = 20
2. x² = V14²-11²
= V196-121
= V75
x = V25×3
= 5V3
3. x² = V9²-7²
= V81-49
= V32
x = V16×2
= 4V2
