12. Explain why is (+5) + (-7) = -2.

Let's use a number line to help us visualize what's going on.

Starting at 0, +5 takes us 5 units to the right.

From there, -7 moves us 7 units back to the left and we end up at -2.

So (+5) + (-7) simplifies to -2.

Take a look at the image below.

7.9m and 4.3°

step-by-step explanation:

let east be +x and north be +y, x = distance * cos θ, y = distance * sin θ  

for 3.5 south, y = -3.5  

for 8.2, x = 8.2 * cos 30 and y = 8.2 * sin 30  

for 15 west, x = -15  

total x = 8.2 * cos 30 – 15 ≈ -7.9  

total y = -3.5 + 8.2 * sin 30 = 0.6  

magnitude = [(8.2 * cos 30 – 15)^2 + 0.6^2)]^0.5  

the magnitude is approximately 7.9 m  

tan θ = y/x = 0.6/-7.9  

the angle is approximately 4.3˚ north of west