Answer:
x = -3.5
Step-by-step explanation:
Simplifying
0.4x + 2.9 = 1.5
Reorder the terms:
2.9 + 0.4x = 1.5
Solving
2.9 + 0.4x = 1.5
Solving for variable 'x'.
Move all terms containing x to the left, all other terms to the right.
Add '-2.9' to each side of the equation.
2.9 + -2.9 + 0.4x = 1.5 + -2.9
Combine like terms: 2.9 + -2.9 = 0.0
0.0 + 0.4x = 1.5 + -2.9
0.4x = 1.5 + -2.9
Combine like terms: 1.5 + -2.9 = -1.4
0.4x = -1.4
Divide each side by '0.4'.
x = -3.5
Simplifying
x = -3.5
All you have to do, is combine like terms. Let's go through it:

Arrange it so you can easily combine like terms:

So, your answer for the sum is 1) 7x² - 10x + 2
Whenever a problem says "one number" and "another number" we can substitute x and y. for this we have x=2y+1 and xy=1. since we know the value of x (2y+1) we can substitute it for the other equation to get (2y+1)y=10. simplify to get 2y^2+y=10. from here you can do a few methods to solve this, but the simplest in my opinion is by factoring.
In order to factor it must be equal to 0, so we have 2y^2+y-10=0. We factor this and get y=5 (we also get y=-4 but it is an extraneous root). now we can plug that into either equation and find that x=2.
this means our two numbers are 5 and 2