What is the formula for calculating two currencies in relation to each other, if their relation to a third currency is known?

Question

Mathematics

Hey!
1 dollar = 77.5 rubles
1 yuan = 11.75 rubles

What formula can be used to calculate if you only know how much rubles cost?
250 dollars = ? yuan

To check the formula = the exchange rate writes 1 dollar = 6.81 yuan

Unsuccessfully tried to convert to kopecks
1 dollar = 77.5 rubles = 7750 kopecks
1 yuan = 11.57 rubles = 1157 kopecks
1/7750 $ = 1 kopeck
1/1157 yuan = 1 kopeck
1/7750 $ = 1/1157 yuan
250/7750 * 1157 = 37.3 yuan I

tried unsuccessfully to make the ratio
1 dollar = 77.5 rubles
1 yuan = 11.57 rubles
$ / yuan = 77.5 / 11 ,57 = 6.69835
$250 = 250 * 6.69835 = 1674 yuan