Question 24710
Read these carefully
d = David's age now
m = Maya's age now
(1) m + 15 = 2 * d
(2) d + 15 = m + 10
from (1)
d = (m + 15) / 2
substituting this in (2)
(m + 15)/2 + 15 = m + 10
multiply through by 2
m + 15 + 30 = 2 * m + 20
subtract m from both sides
subtract 20 from both sides
m = 25
d = (25 + 15) / 2
d = 20
check
20 = (25 + 15) / 2
OK
25 + 15 = 2 * 20
OK