(1)全球通(50+0.15x)元,
快捷通0.3x元;
(2)当x=500时,“全球通”费用=50+0.15×500=125元,“快捷通”费用=0.3×500=150元,
125<150,
∴用“全球通”合算;
(3)当x=180时,“全球通”费用=50+0.15×180=77元,“快捷通”费用=0.3×180=54元,
77>54,
∴用“快捷通”合算.
(1)全球通(50+0.15x)元,
快捷通0.3x元;
(2)当x=500时,“全球通”费用=50+0.15×500=125元,“快捷通”费用=0.3×500=150元,
125<150,
∴用“全球通”合算;
(3)当x=180时,“全球通”费用=50+0.15×180=77元,“快捷通”费用=0.3×180=54元,
77>54,
∴用“快捷通”合算.