Respuesta :

Answer:

285.15

Step-by-step explanation:

Given the expression;

19/258 = 21/x

We are to find the unknown value x;

Cross multiply;

19 * x = 258 * 21

19x = 5418

Divide both sides by 19;

19x/19 = 5418/19

x = 285.15

Hence the unknown value is 285.15