Resposta :
9/7 - 7/9 =
mmc de 7 e 9 = 7x9 = 63
(63:7x9)/63 - (63:9.7)/63 =
81/63 - 49/63 = (81-49)/63 = 32/63
mmc de 7 e 9 = 7x9 = 63
(63:7x9)/63 - (63:9.7)/63 =
81/63 - 49/63 = (81-49)/63 = 32/63