设此同学的化学为x分
化学:x
数学:25.5x
英语:25.5x-25.5
生物:25.5x-25.5-45.5=25.5x-71
语文:3(25.5x-71)+3=76.5x-210
物理:(25.5x+76.5x-210)÷4.5=68x/3-140/3
x+25.5x+25.5x-25.5+25.5x-71+76.5x-210+68x/3-140/3=353.5
x+25.5x+25.5x+25.5x+76.5x+68x/3=353.5+25.5+71+210+140/3
153x+68x/3=660+140/3
459x+68x=1980+140
527x=2120
x≈4