[(x+540:6)* 7-100]:4:5=30
[(x+90)* 7-100]:4=30*5
[(x+90)* 7-100]:4=150
(x+90)* 7-100=150*4
(x+90)* 7-100=600
(x+90)* 7=600+100
(x+909)* 7=700
x+90=700:7
x+90=100
x=100-90
x=10
2.
(1000*68)-(792:4)+1999=68000-198+1999=69801
3.
102*3=306---andreea
84*5=420---mihaela
420-306=114 mihaela are cu 114 timbre mai mult ca andreea