| ⊦ dec_i + dec_j = dec_j + dec_i |
⊦ dec_i + dec_j = mkDecimal(dec_i.int * 10 ^ dec_j.scale + dec_j.int * 10 ^ dec_i.scale, dec_i.scale + dec_j.scale)
⊦ mkDecimal(dec_i.int * 10 ^ dec_j.scale + dec_j.int * 10 ^ dec_i.scale, dec_i.scale + dec_j.scale) = dec_j + dec_i
Used terms: dec_j, dec_i