Answer:
Since many viruses can infect a large number of different cell types, ... An example is potato yellow dwarf virus, which can grow in leafhoppers
1ft=12in
1ft/12in=1
3.5ft=?in
1ft:12in=3.5ft:?in
1ft/12in=3.5ft/?in
times both sides by 12?in
1?=42in
answer is 42 in
or you could just do
3.5 times 12=42 inches