As people age daily stress and worry decrease and Percentage Reporting Stress 60 happiness increases according to an analysis of 340 847 adults ages 18 to 85 in a certain country 40 The graphs show a portion of the research Complete parts a and b below 30 50 20 10 22 Age 62 Percentage Reporting Stress 60 50 890000 40 30 20 10 22 54 62 18 0 15 30 45 60 75 Age G Part 1 of 2 a Find the slope of the line passing through the two points shown in the line graph Express the slope as a decimal Round to one decimal place as needed