In 1948 Melvin Wellman discovered this pretty anagram:

ELEVEN + TWO = TWELVE + ONE

And Dave Morice found this:

THIRTEEN + TWENTY – ONE = (NINETY / TWO) – TEN – THREE

Lee Sallows discovered two similar specimens in Spanish:

UNO + CATORCE = CUATRO + ONCE

DOS + TRECE = TRES + DOCE

These can be combined to make more:

UNO + DOS + TRECE + CATORCE = TRES + CUATRO + ONCE + DOCE

UNO + TRES + DOCE + CATORCE = DOS + CUATRO + ONCE + TRECE