Three children collected a total of 270 used books. Clare collected 25 more used books than Ryan, Jerry collected 19 more used books
than Clare. How many used books did Jerry collect?

111 books

Explanation:

c + r + y = 270    eq. 1

c = r + 25      eq. 2

y = c + 19      eq. 3

c = books collected by Clare

r = books collected by Ryan

y = books collected by Jerry

from the eq. 2:

r =  c - 25     eq. 4

Replacing eq. 4 and eq.3 on eq.1

c + (c-25) + (c+19) = 270

3c + 19 - 25 = 270

3c - 6 = 270

3c = 270 + 6

3c = 276

c = 276/3

c = 92

from eq. 4

r = c - 25

r = 92 - 25

r = 67

from eq. 3

y = c + 19

y = 92 + 19

y = 111

Check:

92 + 67 + 111 = 270

then:

Jerry collect:

111 books