Answer:
Velocity can be directly added or subtracted.
For example, if a boat has a velocity V in still water.
And now you put the boat in a river with a current that has a velocity V'
The total velocity of the boat in that river is just the addition of these two velocities.
Velocity in the river = V + V'
Where the only tricky part is that the velocity is a vector, so you need to take in account the directions of each vector.
In this case, we have a plane with a maximum velocity of 160km, let's assume a direction for this velocity, let's say that is in the positive x-direction.
Then we can write the velocity in the vector form:
velocity = (vel in x-axis, vel in y-axis)
The velocity of the plane can be written as:
v = (160km/h, 0)
Now we add a crosswind of 30km/h
crosswind means that it is perpendicular, then it acts on the y-axis.
Then the total velocity of the plane will be:
velocity = (160km/h, 0) + (0, 30km/h)
velocity = (160km/h, 30km/h)
Now you can compute the total velocity of the airplane as the module of that vector.
Remember that for a vector (x, y) the module is:
mod = √(x^2 + y^2)
Then the module of the velocity is:
v = √( (160km/h)^2 + (30km/h)^2) = 162.8 km/h