A is bigger than B by x vs. x%

How do you say
This number is bigger than that number by 10. This number is bigger than that number by 10%.
in the three Romance languages?

French: Ce nombre est plus grand que ce nombre de 10. Ce nombre est plus grand que ce nombre de 10 %.
Spanish: Este número es mayor que ese número en / por 10. Este número es mayor que ese número en (un) 10%.
Italian: Questo numero è maggiore di quel numero di 10. Questo numero è maggiore di quel numero del 10%.

While English than is clearly translated as que, que, and di, in French, Spanish, and Italian, respectively, the preposition by that indicates the amount of difference has some complications in case of Spanish and Italian. French simply uses de. But Spanish uses en or por for a fixed difference, and en un and less frequently just en for a percentage; think of it as short for en un porcentaje. Italian's del is actually the combined form of di + il, as if it said "by the (percentage)".