Answer:
y = 541
Step-by-step explanation:
The mean is calculated as
mean = [tex]\frac{sum}{count}[/tex]
Mean of set A = [tex]\frac{281+268+225+290}{4}[/tex] = [tex]\frac{1064}{4}[/tex] = 266
ratio between means = 7 : 12, then
mean of set B = [tex]\frac{12}{7}[/tex] × 266 = 456 , thus
[tex]\frac{392+512+413+422+y}{5}[/tex] = 456 ( multiply both sides by 5 )
1739 + y = 2280 ( subtract 1739 from both sides )
y = 541
