Venn diagram 2

[soft hatch]

you can form an equation

with all the information you know

you know the set (all the information on the venn diagram) will equal 26.

(23 - y) + y + (11 - y) + 3 = 26

then solve for y

37 - y = 26

so y = 11

so to work out how many people in the club own both a bike and a surfboard

you're only interested in the middle section

y = both surfboard and bike

y = 11.

done

@kind lotus