design/12914-monotonic: fix a few typos

Change-Id: I139a158a02afd8c78aa77dc39264369dfbc07d37
Reviewed-on: https://go-review.googlesource.com/36254
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/design/12914-monotonic.md b/design/12914-monotonic.md
index 048d2b1..1f3f65e 100644
--- a/design/12914-monotonic.md
+++ b/design/12914-monotonic.md
@@ -9,7 +9,7 @@
 ## Abstract
 
 Comparison and subtraction of times observed by `time.Now` can return incorrect
-results if the system wall clock is reset bewteen the two observations.
+results if the system wall clock is reset between the two observations.
 We propose to extend the `time.Time` representation to hold an
 additional monotonic clock reading for use in those calculations.
 Among other benefits, this should make it impossible for a basic elapsed time
@@ -159,7 +159,7 @@
 over a 20-hour window in which the clock runs at 99.9986% speed
 (20 hours on that clock corresponds to 20 hours and one second
 in the real world).
-In 2011, hoped that the trend toward reliable, reset-free computer clocks
+In 2011, I hoped that the trend toward reliable, reset-free computer clocks
 would continue and that Go programs could safely use the system wall clock
 to measure elapsed times.
 I was wrong.
@@ -359,7 +359,7 @@
 > If Times t and u both contain monotonic clock readings, the operations
 > t.After(u), t.Before(u), t.Equal(u), and t.Sub(u) are carried out using
 > the monotonic clock readings alone, ignoring the wall clock readings.
-> (If either t or u or contains no monotonic clock reading, these operations
+> (If either t or u contains no monotonic clock reading, these operations
 > use the wall clock readings.)
 >
 > Note that the Go == operator includes the monotonic clock reading in its comparison.