Вычисли удобным способом 4+9+6 12+3+7 8+11+2

4+9+6=(4+6)+9=10+9=19 12+3+7=12+(3+7)=12+10=22 8+11+2=(8+2)+11=10+11=21

1) 4+9=13+6 =19 2) 12+3=15+7=22 3) 8+2=10+11=21

54: х + 11 = 800 : 40 54: х+11 = 20  54: х = 20  - 11 54: х = 9 х= 54 : 9  х=6 54 : 6 + 11 = 800: 40 9 + 11 = 20 20=20 х*5  +12*9 = 138 5х + 108 = 138 5х = 138 - 108 5х = 30 х = 30: 5 х=6 6 * 5  + 12*9 = 138 30 +108 = 138 138=138 120 + х*3 = 375 х*3 = 375 - 120 3х = 255 х= 255 : 3 х = 85  120 +  85 *3 =375 120 +255=375 375=375 600 - 120 +х*6 =600 6х = 600-600 + 120 6х =120 х=120: 6 х= 20 600 - 120 + 20*6 = 600 600 - 120  + 120  = 600 600=600 1260 +2х=3000 2х = 3000 - 1260 2х =1740 х=1740 : 2 х= 870 1260 + 2*870 = 3000 1260 +1740=3000 3000=3000

54: х + 11 = 800 : 4054: х+11 = 20  54: х = 20   - 1154: х = 9х= 54 : 9  х= : 6 + 11 = 800: 409 + 11 = 2020=20 х*5   +12*9 = 1385х + 108 = 1385х = 138 - 1085х = 30х = 30: 5х= * 5   + 12*9 = 13830 +108 = 138138=138 120 + х*3 = 375х*3 = 375 - 1203х = 255х= 255 : 3х = 85  +   85 *3 =375120 +255=375375=375 600 - 120 +х*6 =6006х = 600-600 + 1206х =120х=120: 6х= - 120 + 20*6 = 600600 - 120   + 120   = 600600=600 1260 +2х=30002х = 3000 - 12602х =1740х=1740 : 2х= + 2*870 = 30001260 +1740=30003000=3000