The phrase "a number of weak" is not correct as it is incomplete and lacks context.
It could be used in a context where you are discussing a group of weak individuals or weak points, but it needs to be followed by a noun to be meaningful.
Example: "A number of weak arguments were presented during the debate."
Alternatives: "several weak" or "a few weak".
In the 14th century the duchy of Opole-Racibórz split into a number of weak duchies that eventually became fiefs of the Bohemian kings.
It remained unclear whether a country like Italy, which has a number of weak banks and is stuck in recession, would be able to afford another bank rescue.
Hassabis acknowledged that the system has a number of weak points, and that part of the reason for the game against Lee was to gain more information on how to improve in those situations.
However, in a receptor field with irregular emergence of a number of weak, late-flowering plants led to a remarkable increase in cross-pollination, despite an average temporal separation of 7 days.
That was a 6.3 percent increase from 2010, when the lagging economy and a number of weak summer lineups caused sales to drop by as much as 15 percent, the concert industry's first decline in 15 years.
Rather than (or in addition to) hiring one or more advisers to negotiate for you, a number of weak parties who might otherwise be in competition with one another join forces to negotiate in a collective, organized manner with one or more stronger parties.
A number of weaker lines are also present.
Two days later there was a second quake measuring 3.0 and since then a number of weaker quakes have been felt, all centered on the same area, Mr. Beavan reported.
When elite competitors take on a number of weaker opponents in simultaneous exhibitions, the stronger player has to move from board to board and has little time to formulate strategies.
And just as a bell's sound is made up of a fundamental frequency and a number of weaker higher-frequency overtones, the pressure waves in the universe had a "fundamental" of large-size peaks and dips in density and "overtones" of smaller and weaker peaks.
A number of weaker non-specific bands were also produced by the WT pGPfs, similar to those seen previously [13], [14], [19].
