What is ##y+10## when ##y=43##?

##43+10= 53##

There are two pieces of information given.

##y+10## tells us what operation is being done with ##y##.

y will be increased by 10.

The other piece of information is giving a value for ##y## ##y=43##

Replace the y in ##(color(red)(y) +10)## by the value ##color(red)(43)##

##color(red)(43) +10 = 53##

The answer would be different for every different value of y.