13x + 7x - 4x = -40
combine like terms o0n the left
16x = -40
divide both sides by 16
x = -5/2 or -2.5
3/8 + 3/5 = <u>39/40</u> and 39/40 Can't be <em>simplified</em>
<span>1.
P(</span>at least one of the calculators is defective)=
1- P(none of the selected calculators is defective).
2.
P(none of the selected calculators is defective)
=n(ways of selecting 4 non-defective calculators)/n(total selections of 4)
3.
selecting 4 non-defective calculators can be done in C(35, 4) many ways,
where

while, the total number selections of 4 out of 18+35=53 calculators can be done in C(53, 4) many ways,

4. so, P(none of the selected calculators is defective)=

5. P(at least one of the calculators is defective)=
1- P(none of the selected calculators is defective)=1-0.18=0.82
Answer:0.82
Answer:
Step-by-step explanation:
Part 1 is B and part 2 is A