F.3 Maths 要步驟 急 !! ><

1.
let x be the smallest one, then x+2 and x+4 be the other two
x + (x+2) + (x+4) < 49
3x + 6 < 49
3x < 43
x < 43/3
x < 14.33
the largest possible value of x is 13

2.
let x be $2 while 20-x be $5
2x + 5(20-x) >= 85
2x + 100 - 5x >= 85
100 - 3x >= 85
100 - 85 >= 3x
15 >= 3x
5 >= x
thus, the most number of $2 is 5