One third of a number is 0.5 less than 4. Find the number

One third of a number is 0.5 less than 4. Find the number

Let X be the number
4-1/3x=0.5
The solution is x = 10.5

Formula calculation: 80% of a number is 20% more than 3% of 4. Find the number

Let this number be x, then we have:
0.8x-3x/4=0.2;
0.05x=0.2;
x=4;
The number is four

2 times of a number minus 2 / 5 (two fifths) to get 8 / 5 (eight fifths). What's the number? (use equation solution)

Let X be 2x - (2 / 5) = (8 / 5) x = 1, which is 1

Two fifths of a certain number is 10 more than 70. Find a certain number and solve the equation

Let this number be X
2/5x-70=10
2/5x=80
x=200
A: the number is 200