2кг-200г=2000г-200г=1800г=1кг800г
2м-200см=200см-200см=0
1кг500г=1500г
1500×4=6000г
6000г=6кг
7-x>0⇒x<7
3-x>0⇒x<3
x∈(-∞;3)
lo(5)(7-x)=log(5)(15-5x)
7-x=15-5x
-x+5x=15-7
4x=8
x=2
(29+58) - (58-29) = 58; (47-39) + (47+39) = 94; 80-(7*8) = 24; 26+(5*9) = 71; (75-23) - (35-24) = 41; (26+38) + (74-55) = 83; (6*7) + (5*8) = 82; (9*7) - (72:9) = 55