Решаем в обратном порядке
102/3=34
34+11=45
45-40=5
5*5=25
Дима загадал число 25
1/3-1/5 = ( 1 * 5 ) / (3 * 5) - ( 1 * 3 ) / (5 * 3) = 5/15 - 3/15 = 2/15
<span>1/3-1/6 = ( 1 * 2 ) / (3 * 2) - 1 / 6 = 2/6 - 1/6 = 1/6 </span>
<span>1/4-1/7 = ( 1 * 7 ) / ( 4 * 7) - (1 * 4 ) / ( 7 * 4 ) = 7/28 - 4/28 = 3/28
</span>понятно 6 или 7 класс!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
84:3=28
20*3=60 + 8*3= 24 = 84
2x+0.1-4+16x-8x+4.4=0
10x+0.5=0
10x=-0.5
x=-0.05
350+210=560
350-210=140
560:140=4