Ihave to use mental math to solve everything and i'm only in 5th grade and i confused ‍♀️ also i don know what to do

B: 287

D: 300

Step-by-step explanation:

D

d is certainly a lot easier than b.  Start by understanding that 12 = 6 + 6 which you should be able to handle in your head.

6 * 25 + 6*25

150 + 150

300

This is a prized skill. You should practice it all the time. It leads to estimation which is something you should try to do in any math class you take.

B

How about 10 twenty-sixes + 1 twenty-six. Let's see how that works out.

10* 26 + 26

260 + 26

286   You should check to see if that works. Notice that the 2 and the 6 add to 8 which is what they should do if you are multiplying by 11. The end numbers add to the middle one for 3 digits. It get's a little messy when the end two number add to something greater than 10, but that's another story.

the inequality is:

250c+180g≥950

step-by-step explanation:

let c denotes the number of days in a week   miyoko worked as a cryptographer.

and g denotes the number of days in a week she works as a geologist.

now we are given that she earns $250 for every day she works as a cryptographer,and earns $180 for every day she works as a geologist.

now miyoko's goal is to earn more than $950 this week.

hence, the inequality could be represented as:

250c+180g≥950