P=4a=28
S=a×a
a=28/4=7
S=7×7=49(кв. метров)
7,5х-2,46х=202,86
5,04х=202,86
х=202,86:5,04
х=40,25
19/2 - 6/5 = 9 1/2 - 1 1/5 = 9 5/10- 1 2/10 = 8 3/10 ИЛИ 8.3
1)-2x+19=5x-16
-2x-5x=-19-16
-7x=-35
x=5
2)8x-25=3x+20
8x-3x=20+25
5x=45
x=9
3)6-y=3(3y-8)
6-y=9y-24
-9y-y=-24-6
-10y=-30
y=3
4) 5(y+1.2)=7y+4
5y+6=7y+4
5y-7y=4-6
-2y=-2
y=1
5) 4(x-3)=5(x-5)
4x-12=5x-25
4x-5x=-25+12
-x=-13
x=13
6) 3x-17=8x+18
3x-8x=18+17
-5x=35
x=-7
7)11-5y=12-6y
-5y+6y=12-11
y=1
8) 4y+(11.8-y)=3.8-5y
4y+11.8-y=3.8-5y
4y-y+5y=3.8-11.8
8y=-8
y=-1
9) 3x+16=8x-9
3x-8x=-9-16
-5x=-25
x=5
1) 1800+999 = 2799
2) если m=9, то 2799:9 = 311
Ответ: 311.