Alfred is practicing typing. the first time he tested himself, he could type 45 words per minute. after practicing for a week, he could type 48 words per minute. after two weeks he could type 51 words per minute. based on this pattern, predict how fast alfred will be able to type after 4 weeks of practice.

Let x represent weeks and let y represent his words per minute.

x=week - y=words/minute
0 week  -    45 words/min
1 week   -    48 words/min
2 weeks-    51 words/min        
3 weeks-    54 words/min
4 weeks-    57 words/min

The pattern is: as x goes up by 1, y increases by 3. Therefore, by continuing the pattern, after 4 weeks of practice, Alfred will be able to type 57 words/minute.