Grow MeshPart to a certain point by repeat?

###Solution

The reason your code errors is because you need to compare the individual x/y/z axis members of the Vectors.

Secondly, your code would yield indefinitely if it didn't error because 11*1.18 will always be 11*1.18 and so on; therefore, p.Size will never be greater than the target. And you didn't call the wait function.

You need to implement a step variable. A variable that increments each iteration:

local p = script.Parent
local speed = 1.18

if p.Name == "cloud" then
	wait(0.1)
	local step = 1
	repeat
		wait()
		local offset = step * speed
		p.Size = Vector3.new(11 * offset,5 * offset,7 * offset) 
	until p.Size.X > 22 or p.Size.Y > 10 or p.Size.Z > 14
	wait(0.2)
	p.Parent:Destroy()
end

###Alternative

By preference, I would do this using a numerical for loop. Its syntax makes you declare a step variable initially, and the bounds are easy to correspond to numbers:

local p = script.Parent
local speed = 1.18

if p.Name == "cloud" then
	wait(0.1)
	local origin = p.Size
	for step = 1,10 do --start,finish(numbers may be inaccurate)
		local offset = step * speed
		p.Size = origin + Vector3.new(offset,offset,offset)
		wait()
	end
	wait(0.2)
	p.Parent:Destroy()
end