Step-by-step explanation:
m+n = 7
m = 7 - n
mn = 12
(7 - n)n = 12 ( putting value of m )
7n - n² = 12
n² - 7n + 12 = 0
n² - 3n - 4n + 12 = 0
n ( n - 3 ) - 4 ( n - 3 ) = 0
( n - 4 ) ( n - 3 )
n = 4 , 3
m = 7 - n
m = 7 - 4 or 7 - 3
= 3 or 4
m3 + m3
3×3 + 3×3 or 4×3 + 4×3
9+9 or 12 +12
18 or 24