Okay, sorry I posted the question wrong, heres a screenshot of the real one.

Answer:
7.6
14.8
23.2
Step-by-step explanation:
a = 1.6, a = 4, a = 6.8
3a + 2.8 when a = 1.6
= 3(1.6) + 2.8
= 4.8 + 2.8
= 7.6
3a + 2.8 when a = 4
3(4) + 2.8
= 12 + 2.8
= 14.8
3a + 2.8 when a = 6.8
= 3(6.8) + 2.8
= 20.4 + 2.8
= 23.2