Question

❖ᴏɴʟʏ ᴘʀᴏᴘᴇʀ ꜱᴏʟᴠᴇᴅ ᴀɴꜱᴡᴇʀ ᴡɪᴛʜ ɢᴏᴏᴅ ᴇxᴘʟᴀɴᴀɪᴏɴ ɴᴇᴇᴅᴇᴅ
❖ ɴᴏ ꜱᴘᴀᴍᴍɪɴɢ
❖ᴏɴʟʏ ꜰᴏʀ ᴍᴏᴅᴇʀᴀᴛᴏʀꜱ, ʙʀᴀɪɴʟʏ ꜱᴛᴀʀꜱ ᴀɴᴅ ᴏᴛʜᴇʀ ʙᴇꜱᴛ ᴜꜱᴇʀꜱ​​​

Answer 1

Step-by-step explanation:

$9k - 15 = 5 is the answers$

ok

Answer 2

$\bold \red{ \sum_{k=1}^{20} \left(9 k - 15\right)}$

$\small{\color{red}{\left(\sum_{k=1}^{20} \left(9 k - 15\right)\right)}=\color{red}{\left(-6 + 3 + 12 + 21 + 30 + 39 + 48 + 57 + 66 + 75 + 84 + 93 + 102 + 111 + 120 + 129 + 138 + 147 + 156 + 165\right)}}$

$\color{red}{\left(\sum_{k=1}^{20} \left(9 k - 15\right)\right)}=\color{red}{\left(1590\right)}$

Hence,

$\bold \red{\sum_{k=1}^{20} \left(9 k - 15\right)=1590}$