Answer:
An expression for Francisco's age in terms of a is (2a+3)
An expression for Harrison's age in terms of a is (3a-2)
An expression for the sum of all three ages, in terms of a is (6a+1)
Step-by-step explanation:
Let
a -----> Jenna's age
b -----> Francisco's age
c -----> Harrison's age
we know that
Francisco's age is two times Jenna's age plus three years
b=2a+3 -----> equation A
Harrison's age is three times Jenna's age minus two years
c=3a-2 ----> equation B
The sum of all three ages, in terms of a is
(a+b+c) -----> equation C
substitute equation A and equation B in equation C
a+(2a+3)+(3a-2)
Combine like terms
(a+2a+3a)+(3-2)
6a+1
therefore
An expression for Francisco's age in terms of a is (2a+3)
An expression for Harrison's age in terms of a is (3a-2)
An expression for the sum of all three ages, in terms of a is (6a+1)
= 
= 7/4