a) (x+90)*5+700=600*2
5x+450=1200-700
5x=500-450
x=50:5
x=10
b) 3(3x+7)+9=3*16
9x+21=48-9
9x=39-21
x=18:9
x=2
c) (15+75:x)*13+500=38*20
(15+75:x)*13=760-500
(15+75:x)=260:13
75:x=20-15
x=75:5
x=15
d) 6x+4-22=5x+5+78
6x-5x=5+78-4+22
x=101
e) (10x+15+8x+12):5=27
18x+27=27*5
18x=135-27
x=108:18
x=6
f)2{27-2[3x-(7-6)]+3}:4=10
[27-2(3x-1)+3]=10:2*4
27-6x+2+3=20
-6x=20-32
-6x=-12(-1)
x=12:2
x=2