the alignment between the magnetic tape and head in a magnetic tape storage system affects the performance of the system. suppose that 10% of the read operations are degraded by skewed alignments, 5% of the read operations are degraded by off-center alignments , and the remaining read operations are properly aligned. the probability of read error is 0.01 from a skewed alignment, 0.02 from an off-center alignments, and 0.001 from a proper alignment .what is the probability of a read error?

what level of math? also i don't need to be paid if i can you.

you are playing an adventure game on your computer. you come across a troll who won't let you pass and there is no other way to get to the other side of the river except over the bridge he is guarding.

the troll is a nerd. he takes great delight in watching people struggle with his problems. very few get them. he only gives you one chance and then he changes the puzzle. you have to solve this one.

before you are four blocks. they are numbered 11,6, -7,21.

he tells that the answer he wants is minus and between -1 and - 2. you can use +, -, ×, ÷   ( and ) as many times as you like or no times at all. you don't like the way he's looking at you, but you need to cross the bridge. what do you do?