χ 3 = 12 χ 3χ = 4 solution: 2 χ-7.5+7.5 = 8.5+7.52 χ =16 χ = 82 χ 2 =16 χ 2 solution: 65438. 27+27 = 29+27 4 χ = 56 4 χ 4 = 56 4 ψ ψ =14 Exercise 16: Let the Yellow River be χ km long. Yellow River length+difference = Yangtze River length χ+835 = 6299 χ+835-835 = 6299-835 χ = 5464 A: The Yellow River is 5464 kilometers long. Solution: Assume that about χ babies are born every second on average. Number of babies born per second × 60 = Number of babies born per minute 60χ = 30060χ ÷ 60 = 300÷ 60χ = 5 A: About 5 babies are born per second on average. Solution: Suppose that every square meter of grassland can produce χ oxygen every day. Oxygen production per square meter of grass × 5 = oxygen production per square meter of broad-leaved forest ×5 = 75.5χ÷5 = 75.5χ= 15 A: oxygen production per square meter of grass 15. Solution: put a * * * on the χ tube. A barrel