Match each problem (term) with its sum or difference (definition). (12 points)

a
1.
4.23 − 1.621
b
2.
42.3 + 1.621
d
3.
42.3 − 16.21
c
4.
4.23 + 16.21
a.
20.44
b.
43.921
c.
2.609
d.
26.09