На отвертки потратили 160 рублей
Х/6*7=420
х/6=420/7
х=6=60
х=60*6
х=360
х*7*6=420
х*42=420
х=420/42
х=10
18−5(x+3)>1−7x
18-5x-15>1-7x18−5x−15>1−7x
3-5x>1-7x3−5x>1−7x
-5x+7x>1-3−5x+7x>1−3
2x>-22x>−2
x>-2:2x>−2:2
x>-1x>−1
х є (-1;+\infty)(−1;+∞)
1)12 3/7:4 5/6=87/7:29/6=87/7*6/29=18/7=2 4/7
2)8 1/2:14=17/2:1/14=17/28
3)4 2/5-5/8=22/5-5/8=22/5-5/8=176/40-25/40=151/40=3 31/40
4)3 31/40+2 4/7=5+217/280+160/280=5 377/280=6 97/280
5)6 97/280-17/28=1777/280-17/28=1777/280-170/280=1607/280
6)1607/280:33/56=1607/280*56/33=1607/165=9 122/165