3.5-2s-1.8=-1.3

Solution for 3.5-2s-1.8=-1.3 equation:

Simplifying
3.5 + -2s + -1.8 = -1.3

Reorder the terms:
3.5 + -1.8 + -2s = -1.3

Combine like terms: 3.5 + -1.8 = 1.7
1.7 + -2s = -1.3

Solving
1.7 + -2s = -1.3

Solving for variable 's'.

Move all terms containing s to the left, all other terms to the right.

Add '-1.7' to each side of the equation.
1.7 + -1.7 + -2s = -1.3 + -1.7

Combine like terms: 1.7 + -1.7 = 0.0
0.0 + -2s = -1.3 + -1.7
-2s = -1.3 + -1.7

Combine like terms: -1.3 + -1.7 = -3
-2s = -3

Divide each side by '-2'.
s = 1.5

Simplifying
s = 1.5