10: (X-30) = (x + 50): how to solve the equation of X?

10: (X-30) = (x + 50): how to solve the equation of X?

X:(X-30)=(X+50):X
Inner product = outer product
X*X=(X-30)(X+50)
X²=X²+20X-1500
20X=1500
X=1500/20
X=75

The two kinds of steel contain 5% and 40% nickel respectively. In order to get 140 tons of steel with 30% nickel, how many tons of steel with 5% nickel and steel with 40% nickel are needed?

If x tons of steel containing 40% nickel are needed, then 140-x tons of steel containing 5% nickel can be obtained. According to the meaning of the title, the equation is as follows: 5% (140-x) + 40% x = 140 × 30%, & nbsp; & nbsp; & nbsp; 7-0.05x + 0.4x = 42, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 0.35x = 35, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 100, so 140-10 = 40 tons. A: 40 tons of steel with 5% nickel and 100 tons of steel with 40% nickel are required

How to solve the equation (70 + x) divided by (350 + x) = 30%?

(70 + x) divided by (350 + x) = 30%
70+X=0.3(350+X)
70+X=0.3×350+0.3X
X-0.3X=105-70
0.7X=35
X=35÷0.7
X=50