How to Combine Ratios

$b$ is 3 in both ratios, so you can directly combine to get $a:b:c=1:3:4$.

Since $b$ is 7 in both ratios, you can directly combine them to get $a:b:c=4:7:2$.

To combine the ratios, first make the $b$ values equal by finding the LCM of 5 and 2, which is 10. Then scale each ratio: $3:5$ becomes $6:10$, and $2:7$ becomes $10:35$. So the combined ratio is $a:b:c=6:10:35$.

Since green appears in both ratios, match that value first. The LCM of 4 and 2 is 4. Scale red:green $5:2$ to $10:4$, and blue:green $3:4$ stays the same. Be careful with the order: red:green:blue = $10:4:3$.

To combine the ratios, match the value of $y$ since it appears in both ratios. The LCM of 6 and 4 is 12. Scale $7:6$ to $14:12$ and $4:5$ to $12:15$. So the combined ratio is $x:y:z=14:12:15$.

Bananas appear in both ratios, so link them to make one full ratio: apples:bananas:grapes = $5:3:2$. Since 25 apples represent the 5 parts for apples, divide 25 by 5 to find that one part equals 5. Grapes are 2 parts, so $2\times 5=10$ grapes.