I bet you mean
10x+10y+20z=1850
20x+20y+10z=2200
20x+10y+10z=1500
get rid of x and y in first two by multiplying first eqn by 2
20x+20y+40z=3700
................> 30 z = 1500 so z = 50
20x+20y+10z=2200
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then third and first
20x+10y+10z=1500 >> 20 x + 10 y = 1000
20x+20y+40z=3700 >> 20 x + 20 y = 1700
so
-20 y = -700
y = 35
go back and get x from anywhaere knowing y is 35 and z is 50
10x+10y+20=1850
20x+20y+10z=2200
20x+10y+10z=1500
1 answer