23:(6 5/17 +1 12/17) - (4 2/5-2
3/5) :5=23 : 8 - 1 4/5 : 5=2 7/8 - 9/25 =2,875 - 0,36=2,515
400-5х=270-20
400-5х=250
5х=400-250
5х=150
х=150÷5=30
(3x+7y)²=10y
(3x+7y)²=10x
10x=10y
(3x+7y)²=10x
y=x
(3x+7x)²=10x
y=x
(10x)²=10x
y=x
100x²-10x=0
y=x
10x(10x-1)=0
x₁=0 y₁=0
x₂=1/10 y₁=1/10