-10<= 5+x<-5
1) We have the following 2 conditions:
[1]: -10 ≤ 5 + x
[2]: 5 + x < -5
2) Let's solve for x: -10 ≤ 5 + x [1]
5 + x ≥ -10
ⓘ We subtract 5 from both sides
x ≥ -10 -5
ⓘ Start from -10 and move back 5 more on the number line, away from zero: -10 -5 = -15
Solution obtained [1]: x ≥ -15
3) Solving for x: 5 + x < -5 [2] using x ≥ -15
5 + x < -5
ⓘ We subtract 5 from both sides
x < -5 -5
ⓘ Start from -5 and move back 5 more on the number line, away from zero: -5 -5 = -10
Solution found [2]: x < -10
Intersecting x ≥ -15 and x < -10 gives x ∈ [-15, -10)
▶Solution:   x ∈ [-15, -10)